- Linux Ethernet Bonding Driver mini-howto
+ Linux Ethernet Bonding Driver HOWTO
Initial release : Thomas Davis <tadavis at lbl.gov>
Corrections, HA extensions : 2000/10/03-15 :
- Janice Girouard <girouard at us dot ibm dot com>
- Jay Vosburgh <fubar at us dot ibm dot com>
+Reorganized and updated Feb 2005 by Jay Vosburgh
+
Note :
------
+
The bonding driver originally came from Donald Becker's beowulf patches for
kernel 2.0. It has changed quite a bit since, and the original tools from
extreme-linux and beowulf sites will not work with this version of the driver.
For new versions of the driver, patches for older kernels and the updated
userspace tools, please follow the links at the end of this file.
-
Table of Contents
=================
-Installation
-Bond Configuration
-Module Parameters
-Configuring Multiple Bonds
-Switch Configuration
-Verifying Bond Configuration
-Frequently Asked Questions
-High Availability
-Promiscuous Sniffing notes
-8021q VLAN support
-Limitations
-Resources and Links
-
-
-Installation
-============
-
-1) Build kernel with the bonding driver
----------------------------------------
-For the latest version of the bonding driver, use kernel 2.4.12 or above
-(otherwise you will need to apply a patch).
-
-Configure kernel with `make menuconfig/xconfig/config', and select "Bonding
-driver support" in the "Network device support" section. It is recommended
-to configure the driver as module since it is currently the only way to
-pass parameters to the driver and configure more than one bonding device.
-
-Build and install the new kernel and modules.
-
-2) Get and install the userspace tools
---------------------------------------
-This version of the bonding driver requires updated ifenslave program. The
-original one from extreme-linux and beowulf will not work. Kernels 2.4.12
-and above include the updated version of ifenslave.c in
-Documentation/networking directory. For older kernels, please follow the
-links at the end of this file.
-
-IMPORTANT!!! If you are running on Redhat 7.1 or greater, you need
-to be careful because /usr/include/linux is no longer a symbolic link
-to /usr/src/linux/include/linux. If you build ifenslave while this is
-true, ifenslave will appear to succeed but your bond won't work. The purpose
-of the -I option on the ifenslave compile line is to make sure it uses
-/usr/src/linux/include/linux/if_bonding.h instead of the version from
-/usr/include/linux.
-
-To install ifenslave.c, do:
- # gcc -Wall -Wstrict-prototypes -O -I/usr/src/linux/include ifenslave.c -o ifenslave
- # cp ifenslave /sbin/ifenslave
-
-
-Bond Configuration
-==================
+1. Bonding Driver Installation
-You will need to add at least the following line to /etc/modprobe.conf
-so the bonding driver will automatically load when the bond0 interface is
-configured. Refer to the modprobe.conf manual page for specific modprobe.conf
-syntax details. The Module Parameters section of this document describes each
-bonding driver parameter.
+2. Bonding Driver Options
- alias bond0 bonding
+3. Configuring Bonding Devices
+3.1 Configuration with sysconfig support
+3.2 Configuration with initscripts support
+3.3 Configuring Bonding Manually
+3.4 Configuring Multiple Bonds
-Use standard distribution techniques to define the bond0 network interface. For
-example, on modern Red Hat distributions, create an ifcfg-bond0 file in
-the /etc/sysconfig/network-scripts directory that resembles the following:
+5. Querying Bonding Configuration
+5.1 Bonding Configuration
+5.2 Network Configuration
-DEVICE=bond0
-IPADDR=192.168.1.1
-NETMASK=255.255.255.0
-NETWORK=192.168.1.0
-BROADCAST=192.168.1.255
-ONBOOT=yes
-BOOTPROTO=none
-USERCTL=no
+6. Switch Configuration
-(use appropriate values for your network above)
+7. 802.1q VLAN Support
-All interfaces that are part of a bond should have SLAVE and MASTER
-definitions. For example, in the case of Red Hat, if you wish to make eth0 and
-eth1 a part of the bonding interface bond0, their config files (ifcfg-eth0 and
-ifcfg-eth1) should resemble the following:
+8. Link Monitoring
+8.1 ARP Monitor Operation
+8.2 Configuring Multiple ARP Targets
+8.3 MII Monitor Operation
-DEVICE=eth0
-USERCTL=no
-ONBOOT=yes
-MASTER=bond0
-SLAVE=yes
-BOOTPROTO=none
+9. Potential Trouble Sources
+9.1 Adventures in Routing
+9.2 Ethernet Device Renaming
+9.3 Painfully Slow Or No Failed Link Detection By Miimon
-Use DEVICE=eth1 in the ifcfg-eth1 config file. If you configure a second
-bonding interface (bond1), use MASTER=bond1 in the config file to make the
-network interface be a slave of bond1.
+10. SNMP agents
-Restart the networking subsystem or just bring up the bonding device if your
-administration tools allow it. Otherwise, reboot. On Red Hat distros you can
-issue `ifup bond0' or `/etc/rc.d/init.d/network restart'.
+11. Promiscuous mode
-If the administration tools of your distribution do not support
-master/slave notation in configuring network interfaces, you will need to
-manually configure the bonding device with the following commands:
+12. High Availability Information
+12.1 High Availability in a Single Switch Topology
+12.1.1 Bonding Mode Selection for Single Switch Topology
+12.1.2 Link Monitoring for Single Switch Topology
+12.2 High Availability in a Multiple Switch Topology
+12.2.1 Bonding Mode Selection for Multiple Switch Topology
+12.2.2 Link Monitoring for Multiple Switch Topology
+12.3 Switch Behavior Issues for High Availability
- # /sbin/ifconfig bond0 192.168.1.1 netmask 255.255.255.0 \
- broadcast 192.168.1.255 up
+13. Hardware Specific Considerations
+13.1 IBM BladeCenter
- # /sbin/ifenslave bond0 eth0
- # /sbin/ifenslave bond0 eth1
+14. Frequently Asked Questions
-(use appropriate values for your network above)
+15. Resources and Links
-You can then create a script containing these commands and place it in the
-appropriate rc directory.
-If you specifically need all network drivers loaded before the bonding driver,
-adding the following line to modprobe.conf will cause the network driver for
-eth0 and eth1 to be loaded before the bonding driver.
+1. Bonding Driver Installation
+==============================
-install bond0 /sbin/modprobe -a eth0 eth1 && /sbin/modprobe bonding
+ Most popular distro kernels ship with the bonding driver
+already available as a module and the ifenslave user level control
+program installed and ready for use. If your distro does not, or you
+have need to compile bonding from source (e.g., configuring and
+installing a mainline kernel from kernel.org), you'll need to perform
+the following steps:
-Be careful not to reference bond0 itself at the end of the line, or modprobe
-will die in an endless recursive loop.
+1.1 Configure and build the kernel with bonding
+-----------------------------------------------
-If running SNMP agents, the bonding driver should be loaded before any network
-drivers participating in a bond. This requirement is due to the the interface
-index (ipAdEntIfIndex) being associated to the first interface found with a
-given IP address. That is, there is only one ipAdEntIfIndex for each IP
-address. For example, if eth0 and eth1 are slaves of bond0 and the driver for
-eth0 is loaded before the bonding driver, the interface for the IP address
-will be associated with the eth0 interface. This configuration is shown below,
-the IP address 192.168.1.1 has an interface index of 2 which indexes to eth0
-in the ifDescr table (ifDescr.2).
+ The latest version of the bonding driver is available in the
+drivers/net/bonding subdirectory of the most recent kernel source
+(which is available on http://kernel.org).
- interfaces.ifTable.ifEntry.ifDescr.1 = lo
- interfaces.ifTable.ifEntry.ifDescr.2 = eth0
- interfaces.ifTable.ifEntry.ifDescr.3 = eth1
- interfaces.ifTable.ifEntry.ifDescr.4 = eth2
- interfaces.ifTable.ifEntry.ifDescr.5 = eth3
- interfaces.ifTable.ifEntry.ifDescr.6 = bond0
- ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.10.10.10 = 5
- ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.1.1 = 2
- ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.74.20.94 = 4
- ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1
+ Prior to the 2.4.11 kernel, the bonding driver was maintained
+largely outside the kernel tree; patches for some earlier kernels are
+available on the bonding sourceforge site, although those patches are
+still several years out of date. Most users will want to use either
+the most recent kernel from kernel.org or whatever kernel came with
+their distro.
-This problem is avoided by loading the bonding driver before any network
-drivers participating in a bond. Below is an example of loading the bonding
-driver first, the IP address 192.168.1.1 is correctly associated with
-ifDescr.2.
+ Configure kernel with "make menuconfig" (or "make xconfig" or
+"make config"), then select "Bonding driver support" in the "Network
+device support" section. It is recommended that you configure the
+driver as module since it is currently the only way to pass parameters
+to the driver or configure more than one bonding device.
- interfaces.ifTable.ifEntry.ifDescr.1 = lo
- interfaces.ifTable.ifEntry.ifDescr.2 = bond0
- interfaces.ifTable.ifEntry.ifDescr.3 = eth0
- interfaces.ifTable.ifEntry.ifDescr.4 = eth1
- interfaces.ifTable.ifEntry.ifDescr.5 = eth2
- interfaces.ifTable.ifEntry.ifDescr.6 = eth3
- ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.10.10.10 = 6
- ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.1.1 = 2
- ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.74.20.94 = 5
- ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1
+ Build and install the new kernel and modules, then proceed to
+step 2.
-While some distributions may not report the interface name in ifDescr,
-the association between the IP address and IfIndex remains and SNMP
-functions such as Interface_Scan_Next will report that association.
+1.2 Install ifenslave Control Utility
+-------------------------------------
+ The ifenslave user level control program is included in the
+kernel source tree, in the file Documentation/networking/ifenslave.c.
+It is generally recommended that you use the ifenslave that
+corresponds to the kernel that you are using (either from the same
+source tree or supplied with the distro), however, ifenslave
+executables from older kernels should function (but features newer
+than the ifenslave release are not supported). Running an ifenslave
+that is newer than the kernel is not supported, and may or may not
+work.
-Module Parameters
-=================
+ To install ifenslave, do the following:
+
+# gcc -Wall -O -I/usr/src/linux/include ifenslave.c -o ifenslave
+# cp ifenslave /sbin/ifenslave
+
+ If your kernel source is not in "/usr/src/linux," then replace
+"/usr/src/linux/include" in the above with the location of your kernel
+source include directory.
+
+ You may wish to back up any existing /sbin/ifenslave, or, for
+testing or informal use, tag the ifenslave to the kernel version
+(e.g., name the ifenslave executable /sbin/ifenslave-2.6.10).
+
+IMPORTANT NOTE:
-Optional parameters for the bonding driver can be supplied as command line
-arguments to the insmod command. Typically, these parameters are specified in
-the file /etc/modprobe.conf (see the manual page for modprobe.conf). The
-available bonding driver parameters are listed below. If a parameter is not
-specified the default value is used. When initially configuring a bond, it
-is recommended "tail -f /var/log/messages" be run in a separate window to
-watch for bonding driver error messages.
+ If you omit the "-I" or specify an incorrect directory, you
+may end up with an ifenslave that is incompatible with the kernel
+you're trying to build it for. Some distros (e.g., Red Hat from 7.1
+onwards) do not have /usr/include/linux symbolically linked to the
+default kernel source include directory.
-It is critical that either the miimon or arp_interval and arp_ip_target
-parameters be specified, otherwise serious network degradation will occur
-during link failures.
+
+2. Bonding Driver Options
+=========================
+
+ Options for the bonding driver are supplied as parameters to
+the bonding module at load time. They may be given as command line
+arguments to the insmod or modprobe command, but are usually specified
+in either the /etc/modprobe.conf configuration file, or in a
+distro-specific configuration file (some of which are detailed in the
+next section).
+
+ The available bonding driver parameters are listed below. If a
+parameter is not specified the default value is used. When initially
+configuring a bond, it is recommended "tail -f /var/log/messages" be
+run in a separate window to watch for bonding driver error messages.
+
+ It is critical that either the miimon or arp_interval and
+arp_ip_target parameters be specified, otherwise serious network
+degradation will occur during link failures. Very few devices do not
+support at least miimon, so there is really no reason not to use it.
+
+ Options with textual values will accept either the text name
+ or, for backwards compatibility, the option value. E.g.,
+ "mode=802.3ad" and "mode=4" set the same mode.
+
+ The parameters are as follows:
arp_interval
- Specifies the ARP monitoring frequency in milli-seconds.
- If ARP monitoring is used in a load-balancing mode (mode 0 or 2), the
- switch should be configured in a mode that evenly distributes packets
- across all links - such as round-robin. If the switch is configured to
- distribute the packets in an XOR fashion, all replies from the ARP
- targets will be received on the same link which could cause the other
- team members to fail. ARP monitoring should not be used in conjunction
- with miimon. A value of 0 disables ARP monitoring. The default value
- is 0.
+ Specifies the ARP monitoring frequency in milli-seconds. If
+ ARP monitoring is used in a load-balancing mode (mode 0 or 2),
+ the switch should be configured in a mode that evenly
+ distributes packets across all links - such as round-robin. If
+ the switch is configured to distribute the packets in an XOR
+ fashion, all replies from the ARP targets will be received on
+ the same link which could cause the other team members to
+ fail. ARP monitoring should not be used in conjunction with
+ miimon. A value of 0 disables ARP monitoring. The default
+ value is 0.
arp_ip_target
- Specifies the ip addresses to use when arp_interval is > 0. These
- are the targets of the ARP request sent to determine the health of
- the link to the targets. Specify these values in ddd.ddd.ddd.ddd
- format. Multiple ip adresses must be seperated by a comma. At least
- one ip address needs to be given for ARP monitoring to work. The
- maximum number of targets that can be specified is set at 16.
+ Specifies the ip addresses to use when arp_interval is > 0.
+ These are the targets of the ARP request sent to determine the
+ health of the link to the targets. Specify these values in
+ ddd.ddd.ddd.ddd format. Multiple ip adresses must be
+ seperated by a comma. At least one IP address must be given
+ for ARP monitoring to function. The maximum number of targets
+ that can be specified is 16. The default value is no IP
+ addresses.
downdelay
- Specifies the delay time in milli-seconds to disable a link after a
- link failure has been detected. This should be a multiple of miimon
- value, otherwise the value will be rounded. The default value is 0.
+ Specifies the time, in milliseconds, to wait before disabling
+ a slave after a link failure has been detected. This option
+ is only valid for the miimon link monitor. The downdelay
+ value should be a multiple of the miimon value; if not, it
+ will be rounded down to the nearest multiple. The default
+ value is 0.
lacp_rate
- Option specifying the rate in which we'll ask our link partner to
- transmit LACPDU packets in 802.3ad mode. Possible values are:
+ Option specifying the rate in which we'll ask our link partner
+ to transmit LACPDU packets in 802.3ad mode. Possible values
+ are:
slow or 0
Request partner to transmit LACPDUs every 30 seconds (default)
miimon
- Specifies the frequency in milli-seconds that MII link monitoring
- will occur. A value of zero disables MII link monitoring. A value
- of 100 is a good starting point. See High Availability section for
- additional information. The default value is 0.
+ Specifies the frequency in milli-seconds that MII link
+ monitoring will occur. A value of zero disables MII link
+ monitoring. A value of 100 is a good starting point. The
+ use_carrier option, below, affects how the link state is
+ determined. See the High Availability section for additional
+ information. The default value is 0.
mode
Specifies one of the bonding policies. The default is
- round-robin (balance-rr). Possible values are (you can use
- either the text or numeric option):
+ balance-rr (round robin). Possible values are:
balance-rr or 0
- Round-robin policy: Transmit in a sequential order
- from the first available slave through the last. This
- mode provides load balancing and fault tolerance.
+ Round-robin policy: Transmit packets in sequential
+ order from the first available slave through the
+ last. This mode provides load balancing and fault
+ tolerance.
active-backup or 1
Active-backup policy: Only one slave in the bond is
- active. A different slave becomes active if, and only
- if, the active slave fails. The bond's MAC address is
+ active. A different slave becomes active if, and only
+ if, the active slave fails. The bond's MAC address is
externally visible on only one port (network adapter)
to avoid confusing the switch. This mode provides
- fault tolerance.
+ fault tolerance. The primary option affects the
+ behavior of this mode.
balance-xor or 2
XOR policy: Transmit based on [(source MAC address
- XOR'd with destination MAC address) modula slave
- count]. This selects the same slave for each
- destination MAC address. This mode provides load
+ XOR'd with destination MAC address) modulo slave
+ count]. This selects the same slave for each
+ destination MAC address. This mode provides load
balancing and fault tolerance.
broadcast or 3
Broadcast policy: transmits everything on all slave
- interfaces. This mode provides fault tolerance.
+ interfaces. This mode provides fault tolerance.
802.3ad or 4
- IEEE 802.3ad Dynamic link aggregation. Creates aggregation
- groups that share the same speed and duplex settings.
- Transmits and receives on all slaves in the active
- aggregator.
+ IEEE 802.3ad Dynamic link aggregation. Creates
+ aggregation groups that share the same speed and
+ duplex settings. Utilizes all slaves in the active
+ aggregator according to the 802.3ad specification.
Pre-requisites:
- 1. Ethtool support in the base drivers for retrieving the
- speed and duplex of each slave.
+ 1. Ethtool support in the base drivers for retrieving
+ the speed and duplex of each slave.
2. A switch that supports IEEE 802.3ad Dynamic link
aggregation.
+ Most switches will require some type of configuration
+ to enable 802.3ad mode.
+
balance-tlb or 5
- Adaptive transmit load balancing: channel bonding that does
- not require any special switch support. The outgoing
- traffic is distributed according to the current load
- (computed relative to the speed) on each slave. Incoming
- traffic is received by the current slave. If the receiving
- slave fails, another slave takes over the MAC address of
- the failed receiving slave.
+ Adaptive transmit load balancing: channel bonding that
+ does not require any special switch support. The
+ outgoing traffic is distributed according to the
+ current load (computed relative to the speed) on each
+ slave. Incoming traffic is received by the current
+ slave. If the receiving slave fails, another slave
+ takes over the MAC address of the failed receiving
+ slave.
Prerequisite:
balance-alb or 6
- Adaptive load balancing: includes balance-tlb + receive
- load balancing (rlb) for IPV4 traffic and does not require
- any special switch support. The receive load balancing is
- achieved by ARP negotiation. The bonding driver intercepts
- the ARP Replies sent by the server on their way out and
- overwrites the src hw address with the unique hw address of
- one of the slaves in the bond such that different clients
- use different hw addresses for the server.
-
- Receive traffic from connections created by the server is
- also balanced. When the server sends an ARP Request the
- bonding driver copies and saves the client's IP information
- from the ARP. When the ARP Reply arrives from the client,
- its hw address is retrieved and the bonding driver
- initiates an ARP reply to this client assigning it to one
- of the slaves in the bond. A problematic outcome of using
- ARP negotiation for balancing is that each time that an ARP
- request is broadcasted it uses the hw address of the
- bond. Hence, clients learn the hw address of the bond and
- the balancing of receive traffic collapses to the current
- salve. This is handled by sending updates (ARP Replies) to
- all the clients with their assigned hw address such that
- the traffic is redistributed. Receive traffic is also
- redistributed when a new slave is added to the bond and
- when an inactive slave is re-activated. The receive load is
- distributed sequentially (round robin) among the group of
- highest speed slaves in the bond.
-
- When a link is reconnected or a new slave joins the bond
- the receive traffic is redistributed among all active
- slaves in the bond by intiating ARP Replies with the
- selected mac address to each of the clients. The updelay
- modeprobe parameter must be set to a value equal or greater
- than the switch's forwarding delay so that the ARP Replies
- sent to the clients will not be blocked by the switch.
+ Adaptive load balancing: includes balance-tlb plus
+ receive load balancing (rlb) for IPV4 traffic, and
+ does not require any special switch support. The
+ receive load balancing is achieved by ARP negotiation.
+ The bonding driver intercepts the ARP Replies sent by
+ the local system on their way out and overwrites the
+ source hardware address with the unique hardware
+ address of one of the slaves in the bond such that
+ different peers use different hardware addresses for
+ the server.
+
+ Receive traffic from connections created by the server
+ is also balanced. When the local system sends an ARP
+ Request the bonding driver copies and saves the peer's
+ IP information from the ARP packet. When the ARP
+ Reply arrives from the peer, its hardware address is
+ retrieved and the bonding driver initiates an ARP
+ reply to this peer assigning it to one of the slaves
+ in the bond. A problematic outcome of using ARP
+ negotiation for balancing is that each time that an
+ ARP request is broadcast it uses the hardware address
+ of the bond. Hence, peers learn the hardware address
+ of the bond and the balancing of receive traffic
+ collapses to the current slave. This is handled by
+ sending updates (ARP Replies) to all the peers with
+ their individually assigned hardware address such that
+ the traffic is redistributed. Receive traffic is also
+ redistributed when a new slave is added to the bond
+ and when an inactive slave is re-activated. The
+ receive load is distributed sequentially (round robin)
+ among the group of highest speed slaves in the bond.
+
+ When a link is reconnected or a new slave joins the
+ bond the receive traffic is redistributed among all
+ active slaves in the bond by intiating ARP Replies
+ with the selected mac address to each of the
+ clients. The updelay parameter (detailed below) must
+ be set to a value equal or greater than the switch's
+ forwarding delay so that the ARP Replies sent to the
+ peers will not be blocked by the switch.
Prerequisites:
- 1. Ethtool support in the base drivers for retrieving the
- speed of each slave.
+ 1. Ethtool support in the base drivers for retrieving
+ the speed of each slave.
- 2. Base driver support for setting the hw address of a
- device also when it is open. This is required so that there
- will always be one slave in the team using the bond hw
- address (the curr_active_slave) while having a unique hw
- address for each slave in the bond. If the curr_active_slave
- fails it's hw address is swapped with the new curr_active_slave
- that was chosen.
+ 2. Base driver support for setting the hardware
+ address of a device while it is open. This is
+ required so that there will always be one slave in the
+ team using the bond hardware address (the
+ curr_active_slave) while having a unique hardware
+ address for each slave in the bond. If the
+ curr_active_slave fails its hardware address is
+ swapped with the new curr_active_slave that was
+ chosen.
primary
- A string (eth0, eth2, etc) to equate to a primary device. If this
- value is entered, and the device is on-line, it will be used first
- as the output media. Only when this device is off-line, will
- alternate devices be used. Otherwise, once a failover is detected
- and a new default output is chosen, it will remain the output media
- until it too fails. This is useful when one slave was preferred
- over another, i.e. when one slave is 1000Mbps and another is
- 100Mbps. If the 1000Mbps slave fails and is later restored, it may
- be preferred the faster slave gracefully become the active slave -
- without deliberately failing the 100Mbps slave. Specifying a
- primary is only valid in active-backup mode.
+ A string (eth0, eth2, etc) specifying which slave is the
+ primary device. The specified device will always be the
+ active slave while it is available. Only when the primary is
+ off-line will alternate devices be used. This is useful when
+ one slave is preferred over another, e.g., when one slave has
+ higher throughput than another.
+
+ The primary option is only valid for active-backup mode.
updelay
- Specifies the delay time in milli-seconds to enable a link after a
- link up status has been detected. This should be a multiple of miimon
- value, otherwise the value will be rounded. The default value is 0.
+ Specifies the time, in milliseconds, to wait before enabling a
+ slave after a link recovery has been detected. This option is
+ only valid for the miimon link monitor. The updelay value
+ should be a multiple of the miimon value; if not, it will be
+ rounded down to the nearest multiple. The default value is 0.
use_carrier
- Specifies whether or not miimon should use MII or ETHTOOL
- ioctls vs. netif_carrier_ok() to determine the link status.
- The MII or ETHTOOL ioctls are less efficient and utilize a
- deprecated calling sequence within the kernel. The
- netif_carrier_ok() relies on the device driver to maintain its
- state with netif_carrier_on/off; at this writing, most, but
- not all, device drivers support this facility.
-
- If bonding insists that the link is up when it should not be,
- it may be that your network device driver does not support
- netif_carrier_on/off. This is because the default state for
- netif_carrier is "carrier on." In this case, disabling
- use_carrier will cause bonding to revert to the MII / ETHTOOL
- ioctl method to determine the link state.
-
- A value of 1 enables the use of netif_carrier_ok(), a value of
- 0 will use the deprecated MII / ETHTOOL ioctls. The default
- value is 1.
-
-
-Configuring Multiple Bonds
-==========================
-
-If several bonding interfaces are required, either specify the max_bonds
-parameter (described above), or load the driver multiple times. Using
-the max_bonds parameter is less complicated, but has the limitation that
-all bonding instances created will have the same options. Loading the
-driver multiple times allows each instance of the driver to have differing
-options.
-
-For example, to configure two bonding interfaces, one with mii link
-monitoring performed every 100 milliseconds, and one with ARP link
-monitoring performed every 200 milliseconds, the /etc/conf.modules should
-resemble the following:
+ Specifies whether or not miimon should use MII or ETHTOOL
+ ioctls vs. netif_carrier_ok() to determine the link
+ status. The MII or ETHTOOL ioctls are less efficient and
+ utilize a deprecated calling sequence within the kernel. The
+ netif_carrier_ok() relies on the device driver to maintain its
+ state with netif_carrier_on/off; at this writing, most, but
+ not all, device drivers support this facility.
+
+ If bonding insists that the link is up when it should not be,
+ it may be that your network device driver does not support
+ netif_carrier_on/off. The default state for netif_carrier is
+ "carrier on," so if a driver does not support netif_carrier,
+ it will appear as if the link is always up. In this case,
+ setting use_carrier to 0 will cause bonding to revert to the
+ MII / ETHTOOL ioctl method to determine the link state.
+
+ A value of 1 enables the use of netif_carrier_ok(), a value of
+ 0 will use the deprecated MII / ETHTOOL ioctls. The default
+ value is 1.
-alias bond0 bonding
-alias bond1 bonding
-options bond0 miimon=100
-options bond1 -o bonding1 arp_interval=200 arp_ip_target=10.0.0.1
-Configuring Multiple ARP Targets
-================================
+3. Configuring Bonding Devices
+==============================
-While ARP monitoring can be done with just one target, it can be useful
-in a High Availability setup to have several targets to monitor. In the
-case of just one target, the target itself may go down or have a problem
-making it unresponsive to ARP requests. Having an additional target (or
-several) increases the reliability of the ARP monitoring.
+ There are, essentially, two methods for configuring bonding:
+with support from the distro's network initialization scripts, and
+without. Distros generally use one of two packages for the network
+initialization scripts: initscripts or sysconfig. Recent versions of
+these packages have support for bonding, while older versions do not.
+
+ We will first describe the options for configuring bonding for
+distros using versions of initscripts and sysconfig with full or
+partial support for bonding, then provide information on enabling
+bonding without support from the network initialization scripts (i.e.,
+older versions of initscripts or sysconfig).
-Multiple ARP targets must be seperated by commas as follows:
+ If you're unsure whether your distro uses sysconfig or
+initscripts, or don't know if it's new enough, have no fear.
+Determining this is fairly straightforward.
-# example options for ARP monitoring with three targets
-alias bond0 bonding
-options bond0 arp_interval=60 arp_ip_target=192.168.0.1,192.168.0.3,192.168.0.9
+ First, issue the command:
+
+$ rpm -qf /sbin/ifup
-For just a single target the options would resemble:
+ It will respond with a line of text starting with either
+"initscripts" or "sysconfig," followed by some numbers. This is the
+package that provides your network initialization scripts.
-# example options for ARP monitoring with one target
-alias bond0 bonding
-options bond0 arp_interval=60 arp_ip_target=192.168.0.100
+ Next, to determine if your installation supports bonding,
+issue the command:
-Potential Problems When Using ARP Monitor
-=========================================
+$ grep ifenslave /sbin/ifup
-1. Driver support
+ If this returns any matches, then your initscripts or
+sysconfig has support for bonding.
-The ARP monitor relies on the network device driver to maintain two
-statistics: the last receive time (dev->last_rx), and the last
-transmit time (dev->trans_start). If the network device driver does
-not update one or both of these, then the typical result will be that,
-upon startup, all links in the bond will immediately be declared down,
-and remain that way. A network monitoring tool (tcpdump, e.g.) will
-show ARP requests and replies being sent and received on the bonding
-device.
+3.1 Configuration with sysconfig support
+----------------------------------------
-The possible resolutions for this are to (a) fix the device driver, or
-(b) discontinue the ARP monitor (using miimon as an alternative, for
-example).
+ This section applies to distros using a version of sysconfig
+with bonding support, for example, SuSE Linux Enterprise Server 9.
-2. Adventures in Routing
+ SuSE SLES 9's networking configuration system does support
+bonding, however, at this writing, the YaST system configuration
+frontend does not provide any means to work with bonding devices.
+Bonding devices can be managed by hand, however, as follows.
-When bonding is set up with the ARP monitor, it is important that the
-slave devices not have routes that supercede routes of the master (or,
-generally, not have routes at all). For example, suppose the bonding
-device bond0 has two slaves, eth0 and eth1, and the routing table is
-as follows:
+ First, if they have not already been configured, configure the
+slave devices. On SLES 9, this is most easily done by running the
+yast2 sysconfig configuration utility. The goal is for to create an
+ifcfg-id file for each slave device. The simplest way to accomplish
+this is to configure the devices for DHCP. The name of the
+configuration file for each device will be of the form:
-Kernel IP routing table
-Destination Gateway Genmask Flags MSS Window irtt Iface
-10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth0
-10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth1
-10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 bond0
-127.0.0.0 0.0.0.0 255.0.0.0 U 40 0 0 lo
+ifcfg-id-xx:xx:xx:xx:xx:xx
-In this case, the ARP monitor (and ARP itself) may become confused,
-because ARP requests will be sent on one interface (bond0), but the
-corresponding reply will arrive on a different interface (eth0). This
-reply looks to ARP as an unsolicited ARP reply (because ARP matches
-replies on an interface basis), and is discarded. This will likely
-still update the receive/transmit times in the driver, but will lose
-packets.
-
-The resolution here is simply to insure that slaves do not have routes
-of their own, and if for some reason they must, those routes do not
-supercede routes of their master. This should generally be the case,
-but unusual configurations or errant manual or automatic static route
-additions may cause trouble.
-
-Switch Configuration
-====================
+ Where the "xx" portion will be replaced with the digits from
+the device's permanent MAC address.
-While the switch does not need to be configured when the active-backup,
-balance-tlb or balance-alb policies (mode=1,5,6) are used, it does need to
-be configured for the round-robin, XOR, broadcast, or 802.3ad policies
-(mode=0,2,3,4).
+ Once the set of ifcfg-id-xx:xx:xx:xx:xx:xx files has been
+created, it is necessary to edit the configuration files for the slave
+devices (the MAC addresses correspond to those of the slave devices).
+Before editing, the file will contain muliple lines, and will look
+something like this:
+BOOTPROTO='dhcp'
+STARTMODE='on'
+USERCTL='no'
+UNIQUE='XNzu.WeZGOGF+4wE'
+_nm_name='bus-pci-0001:61:01.0'
-Verifying Bond Configuration
-============================
+ Change the BOOTPROTO and STARTMODE lines to the following:
-1) Bonding information files
-----------------------------
-The bonding driver information files reside in the /proc/net/bonding directory.
+BOOTPROTO='none'
+STARTMODE='off'
+
+ Do not alter the UNIQUE or _nm_name lines. Remove any other
+lines (USERCTL, etc).
+
+ Once the ifcfg-id-xx:xx:xx:xx:xx:xx files have been modified,
+it's time to create the configuration file for the bonding device
+itself. This file is named ifcfg-bondX, where X is the number of the
+bonding device to create, starting at 0. The first such file is
+ifcfg-bond0, the second is ifcfg-bond1, and so on. The sysconfig
+network configuration system will correctly start multiple instances
+of bonding.
+
+ The contents of the ifcfg-bondX file is as follows:
+
+BOOTPROTO="static"
+BROADCAST="10.0.2.255"
+IPADDR="10.0.2.10"
+NETMASK="255.255.0.0"
+NETWORK="10.0.2.0"
+REMOTE_IPADDR=""
+STARTMODE="onboot"
+BONDING_MASTER="yes"
+BONDING_MODULE_OPTS="mode=active-backup miimon=100"
+BONDING_SLAVE0="eth0"
+BONDING_SLAVE1="eth1"
+
+ Replace the sample BROADCAST, IPADDR, NETMASK and NETWORK
+values with the appropriate values for your network.
+
+ Note that configuring the bonding device with BOOTPROTO='dhcp'
+does not work; the scripts attempt to obtain the device address from
+DHCP prior to adding any of the slave devices. Without active slaves,
+the DHCP requests are not sent to the network.
+
+ The STARTMODE specifies when the device is brought online.
+The possible values are:
+
+ onboot: The device is started at boot time. If you're not
+ sure, this is probably what you want.
+
+ manual: The device is started only when ifup is called
+ manually. Bonding devices may be configured this
+ way if you do not wish them to start automatically
+ at boot for some reason.
+
+ hotplug: The device is started by a hotplug event. This is not
+ a valid choice for a bonding device.
+
+ off or ignore: The device configuration is ignored.
+
+ The line BONDING_MASTER='yes' indicates that the device is a
+bonding master device. The only useful value is "yes."
+
+ The contents of BONDING_MODULE_OPTS are supplied to the
+instance of the bonding module for this device. Specify the options
+for the bonding mode, link monitoring, and so on here. Do not include
+the max_bonds bonding parameter; this will confuse the configuration
+system if you have multiple bonding devices.
+
+ Finally, supply one BONDING_SLAVEn="ethX" for each slave,
+where "n" is an increasing value, one for each slave, and "ethX" is
+the name of the slave device (eth0, eth1, etc).
-Sample contents of /proc/net/bonding/bond0 after the driver is loaded with
-parameters of mode=0 and miimon=1000 is shown below.
+ When all configuration files have been modified or created,
+networking must be restarted for the configuration changes to take
+effect. This can be accomplished via the following:
+# /etc/init.d/network restart
+
+ Note that the network control script (/sbin/ifdown) will
+remove the bonding module as part of the network shutdown processing,
+so it is not necessary to remove the module by hand if, e.g., the
+module paramters have changed.
+
+ Also, at this writing, YaST/YaST2 will not manage bonding
+devices (they do not show bonding interfaces on its list of network
+devices). It is necessary to edit the configuration file by hand to
+change the bonding configuration.
+
+ Additional general options and details of the ifcfg file
+format can be found in an example ifcfg template file:
+
+/etc/sysconfig/network/ifcfg.template
+
+ Note that the template does not document the various BONDING_
+settings described above, but does describe many of the other options.
+
+3.2 Configuration with initscripts support
+------------------------------------------
+
+ This section applies to distros using a version of initscripts
+with bonding support, for example, Red Hat Linux 9 or Red Hat
+Enterprise Linux version 3. On these systems, the network
+initialization scripts have some knowledge of bonding, and can be
+configured to control bonding devices.
+
+ These distros will not automatically load the network adapter
+driver unless the ethX device is configured with an IP address.
+Because of this constraint, users must manually configure a
+network-script file for all physical adapters that will be members of
+a bondX link. Network script files are located in the directory:
+
+/etc/sysconfig/network-scripts
+
+ The file name must be prefixed with "ifcfg-eth" and suffixed
+with the adapter's physical adapter number. For example, the script
+for eth0 would be named /etc/sysconfig/network-scripts/ifcfg-eth0.
+Place the following text in the file:
+
+DEVICE=eth0
+USERCTL=no
+ONBOOT=yes
+MASTER=bond0
+SLAVE=yes
+BOOTPROTO=none
+
+ The DEVICE= line will be different for every ethX device and
+must correspond with the name of the file, i.e., ifcfg-eth1 must have
+a device line of DEVICE=eth1. The setting of the MASTER= line will
+also depend on the final bonding interface name chosen for your bond.
+As with other network devices, these typically start at 0, and go up
+one for each device, i.e., the first bonding instance is bond0, the
+second is bond1, and so on.
+
+ Next, create a bond network script. The file name for this
+script will be /etc/sysconfig/network-scripts/ifcfg-bondX where X is
+the number of the bond. For bond0 the file is named "ifcfg-bond0",
+for bond1 it is named "ifcfg-bond1", and so on. Within that file,
+place the following text:
+
+DEVICE=bond0
+IPADDR=192.168.1.1
+NETMASK=255.255.255.0
+NETWORK=192.168.1.0
+BROADCAST=192.168.1.255
+ONBOOT=yes
+BOOTPROTO=none
+USERCTL=no
+
+ Be sure to change the networking specific lines (IPADDR,
+NETMASK, NETWORK and BROADCAST) to match your network configuration.
+
+ Finally, it is necessary to edit /etc/modules.conf to load the
+bonding module when the bond0 interface is brought up. The following
+sample lines in /etc/modules.conf will load the bonding module, and
+select its options:
+
+alias bond0 bonding
+options bond0 mode=balance-alb miimon=100
+
+ Replace the sample parameters with the appropriate set of
+options for your configuration.
+
+ Finally run "/etc/rc.d/init.d/network restart" as root. This
+will restart the networking subsystem and your bond link should be now
+up and running.
+
+
+3.3 Configuring Bonding Manually
+--------------------------------
+
+ This section applies to distros whose network initialization
+scripts (the sysconfig or initscripts package) do not have specific
+knowledge of bonding. One such distro is SuSE Linux Enterprise Server
+version 8.
+
+ The general methodology for these systems is to place the
+bonding module parameters into /etc/modprobe.conf, then add modprobe
+and/or ifenslave commands to the system's global init script. The
+name of the global init script differs; for sysconfig, it is
+/etc/init.d/boot.local and for initscripts it is /etc/rc.d/rc.local.
+
+ For example, if you wanted to make a simple bond of two e100
+devices (presumed to be eth0 and eth1), and have it persist across
+reboots, edit the appropriate file (/etc/init.d/boot.local or
+/etc/rc.d/rc.local), and add the following:
+
+modprobe bonding -obond0 mode=balance-alb miimon=100
+modprobe e100
+ifconfig bond0 192.168.1.1 netmask 255.255.255.0 up
+ifenslave bond0 eth0
+ifenslave bond0 eth1
+
+ Replace the example bonding module parameters and bond0
+network configuration (IP address, netmask, etc) with the appropriate
+values for your configuration. The above example loads the bonding
+module with the name "bond0," this simplifies the naming if multiple
+bonding modules are loaded (each successive instance of the module is
+given a different name, and the module instance names match the
+bonding interface names).
+
+ Unfortunately, this method will not provide support for the
+ifup and ifdown scripts on the bond devices. To reload the bonding
+configuration, it is necessary to run the initialization script, e.g.,
+
+# /etc/init.d/boot.local
+
+ or
+
+# /etc/rc.d/rc.local
+
+ It may be desirable in such a case to create a separate script
+which only initializes the bonding configuration, then call that
+separate script from within boot.local. This allows for bonding to be
+enabled without re-running the entire global init script.
+
+ To shut down the bonding devices, it is necessary to first
+mark the bonding device itself as being down, then remove the
+appropriate device driver modules. For our example above, you can do
+the following:
+
+# ifconfig bond0 down
+# rmmod bond0
+# rmmod e100
+
+ Again, for convenience, it may be desirable to create a script
+with these commands.
+
+
+3.4 Configuring Multiple Bonds
+------------------------------
+
+ This section contains information on configuring multiple
+bonding devices with differing options. If you require multiple
+bonding devices, but all with the same options, see the "max_bonds"
+module paramter, documented above.
+
+ To create multiple bonding devices with differing options, it
+is necessary to load the bonding driver multiple times. Note that
+current versions of the sysconfig network initialization scripts
+handle this automatically; if your distro uses these scripts, no
+special action is needed. See the section Configuring Bonding
+Devices, above, if you're not sure about your network initialization
+scripts.
+
+ To load multiple instances of the module, it is necessary to
+specify a different name for each instance (the module loading system
+requires that every loaded module, even multiple instances of the same
+module, have a unique name). This is accomplished by supplying
+multiple sets of bonding options in /etc/modprobe.conf, for example:
+
+alias bond0 bonding
+options bond0 -o bond0 mode=balance-rr miimon=100
+
+alias bond1 bonding
+options bond1 -o bond1 mode=balance-alb miimon=50
+
+ will load the bonding module two times. The first instance is
+named "bond0" and creates the bond0 device in balance-rr mode with an
+miimon of 100. The second instance is named "bond1" and creates the
+bond1 device in balance-alb mode with an miimon of 50.
+
+ This may be repeated any number of times, specifying a new and
+unique name in place of bond0 or bond1 for each instance.
+
+ When the appropriate module paramters are in place, then
+configure bonding according to the instructions for your distro.
+
+5. Querying Bonding Configuration
+=================================
+
+5.1 Bonding Configuration
+-------------------------
+
+ Each bonding device has a read-only file residing in the
+/proc/net/bonding directory. The file contents include information
+about the bonding configuration, options and state of each slave.
+
+ For example, the contents of /proc/net/bonding/bond0 after the
+driver is loaded with parameters of mode=0 and miimon=1000 is
+generally as follows:
+
+ Ethernet Channel Bonding Driver: 2.6.1 (October 29, 2004)
Bonding Mode: load balancing (round-robin)
Currently Active Slave: eth0
MII Status: up
MII Status: up
Link Failure Count: 1
-2) Network verification
------------------------
-The network configuration can be verified using the ifconfig command. In
-the example below, the bond0 interface is the master (MASTER) while eth0 and
-eth1 are slaves (SLAVE). Notice all slaves of bond0 have the same MAC address
-(HWaddr) as bond0 for all modes except TLB and ALB that require a unique MAC
-address for each slave.
+ The precise format and contents will change depending upon the
+bonding configuration, state, and version of the bonding driver.
+
+5.2 Network configuration
+-------------------------
+
+ The network configuration can be inspected using the ifconfig
+command. Bonding devices will have the MASTER flag set; Bonding slave
+devices will have the SLAVE flag set. The ifconfig output does not
+contain information on which slaves are associated with which masters.
+
+ In the example below, the bond0 interface is the master
+(MASTER) while eth0 and eth1 are slaves (SLAVE). Notice all slaves of
+bond0 have the same MAC address (HWaddr) as bond0 for all modes except
+TLB and ALB that require a unique MAC address for each slave.
-[root]# /sbin/ifconfig
+# /sbin/ifconfig
bond0 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4
inet addr:XXX.XXX.XXX.YYY Bcast:XXX.XXX.XXX.255 Mask:255.255.252.0
UP BROADCAST RUNNING MASTER MULTICAST MTU:1500 Metric:1
collisions:0 txqueuelen:100
Interrupt:9 Base address:0x1400
+6. Switch Configuration
+=======================
+
+ For this section, "switch" refers to whatever system the
+bonded devices are directly connected to (i.e., where the other end of
+the cable plugs into). This may be an actual dedicated switch device,
+or it may be another regular system (e.g., another computer running
+Linux),
+
+ The active-backup, balance-tlb and balance-alb modes do not
+require any specific configuration of the switch.
+
+ The 802.3ad mode requires that the switch have the appropriate
+ports configured as an 802.3ad aggregation. The precise method used
+to configure this varies from switch to switch, but, for example, a
+Cisco 3550 series switch requires that the appropriate ports first be
+grouped together in a single etherchannel instance, then that
+etherchannel is set to mode "lacp" to enable 802.3ad (instead of
+standard EtherChannel).
+
+ The balance-rr, balance-xor and broadcast modes generally
+require that the switch have the appropriate ports grouped together.
+The nomenclature for such a group differs between switches, it may be
+called an "etherchannel" (as in the Cisco example, above), a "trunk
+group" or some other similar variation. For these modes, each switch
+will also have its own configuration options for the switch's transmit
+policy to the bond. Typical choices include XOR of either the MAC or
+IP addresses. The transmit policy of the two peers does not need to
+match. For these three modes, the bonding mode really selects a
+transmit policy for an EtherChannel group; all three will interoperate
+with another EtherChannel group.
+
+
+7. 802.1q VLAN Support
+======================
+
+ It is possible to configure VLAN devices over a bond interface
+using the 8021q driver. However, only packets coming from the 8021q
+driver and passing through bonding will be tagged by default. Self
+generated packets, for example, bonding's learning packets or ARP
+packets generated by either ALB mode or the ARP monitor mechanism, are
+tagged internally by bonding itself. As a result, bonding must
+"learn" the VLAN IDs configured above it, and use those IDs to tag
+self generated packets.
+
+ For reasons of simplicity, and to support the use of adapters
+that can do VLAN hardware acceleration offloding, the bonding
+interface declares itself as fully hardware offloaing capable, it gets
+the add_vid/kill_vid notifications to gather the necessary
+information, and it propagates those actions to the slaves. In case
+of mixed adapter types, hardware accelerated tagged packets that
+should go through an adapter that is not offloading capable are
+"un-accelerated" by the bonding driver so the VLAN tag sits in the
+regular location.
+
+ VLAN interfaces *must* be added on top of a bonding interface
+only after enslaving at least one slave. The bonding interface has a
+hardware address of 00:00:00:00:00:00 until the first slave is added.
+If the VLAN interface is created prior to the first enslavement, it
+would pick up the all-zeroes hardware address. Once the first slave
+is attached to the bond, the bond device itself will pick up the
+slave's hardware address, which is then available for the VLAN device.
+
+ Also, be aware that a similar problem can occur if all slaves
+are released from a bond that still has one or more VLAN interfaces on
+top of it. When a new slave is added, the bonding interface will
+obtain its hardware address from the first slave, which might not
+match the hardware address of the VLAN interfaces (which was
+ultimately copied from an earlier slave).
+
+ There are two methods to insure that the VLAN device operates
+with the correct hardware address if all slaves are removed from a
+bond interface:
+
+ 1. Remove all VLAN interfaces then recreate them
+
+ 2. Set the bonding interface's hardware address so that it
+matches the hardware address of the VLAN interfaces.
+
+ Note that changing a VLAN interface's HW address would set the
+underlying device -- i.e. the bonding interface -- to promiscouos
+mode, which might not be what you want.
+
+
+8. Link Monitoring
+==================
-Frequently Asked Questions
-==========================
-
-1. Is it SMP safe?
-
- Yes. The old 2.0.xx channel bonding patch was not SMP safe.
- The new driver was designed to be SMP safe from the start.
-
-2. What type of cards will work with it?
-
- Any Ethernet type cards (you can even mix cards - a Intel
- EtherExpress PRO/100 and a 3com 3c905b, for example).
- You can even bond together Gigabit Ethernet cards!
-
-3. How many bonding devices can I have?
-
- There is no limit.
-
-4. How many slaves can a bonding device have?
-
- Limited by the number of network interfaces Linux supports and/or the
- number of network cards you can place in your system.
-
-5. What happens when a slave link dies?
+ The bonding driver at present supports two schemes for
+monitoring a slave device's link state: the ARP monitor and the MII
+monitor.
+
+ At the present time, due to implementation restrictions in the
+bonding driver itself, it is not possible to enable both ARP and MII
+monitoring simultaneously.
+
+8.1 ARP Monitor Operation
+-------------------------
+
+ The ARP monitor operates as its name suggests: it sends ARP
+queries to one or more designated peer systems on the network, and
+uses the response as an indication that the link is operating. This
+gives some assurance that traffic is actually flowing to and from one
+or more peers on the local network.
+
+ The ARP monitor relies on the device driver itself to verify
+that traffic is flowing. In particular, the driver must keep up to
+date the last receive time, dev->last_rx, and transmit start time,
+dev->trans_start. If these are not updated by the driver, then the
+ARP monitor will immediately fail any slaves using that driver, and
+those slaves will stay down. If networking monitoring (tcpdump, etc)
+shows the ARP requests and replies on the network, then it may be that
+your device driver is not updating last_rx and trans_start.
+
+8.2 Configuring Multiple ARP Targets
+------------------------------------
- If your ethernet cards support MII or ETHTOOL link status monitoring
- and the MII monitoring has been enabled in the driver (see description
- of module parameters), there will be no adverse consequences. This
- release of the bonding driver knows how to get the MII information and
- enables or disables its slaves according to their link status.
- See section on High Availability for additional information.
-
- For ethernet cards not supporting MII status, the arp_interval and
- arp_ip_target parameters must be specified for bonding to work
- correctly. If packets have not been sent or received during the
- specified arp_interval duration, an ARP request is sent to the
- targets to generate send and receive traffic. If after this
- interval, either the successful send and/or receive count has not
- incremented, the next slave in the sequence will become the active
- slave.
-
- If neither mii_monitor and arp_interval is configured, the bonding
- driver will not handle this situation very well. The driver will
- continue to send packets but some packets will be lost. Retransmits
- will cause serious degradation of performance (in the case when one
- of two slave links fails, 50% packets will be lost, which is a serious
- problem for both TCP and UDP).
+ While ARP monitoring can be done with just one target, it can
+be useful in a High Availability setup to have several targets to
+monitor. In the case of just one target, the target itself may go
+down or have a problem making it unresponsive to ARP requests. Having
+an additional target (or several) increases the reliability of the ARP
+monitoring.
-6. Can bonding be used for High Availability?
+ Multiple ARP targets must be seperated by commas as follows:
- Yes, if you use MII monitoring and ALL your cards support MII link
- status reporting. See section on High Availability for more
- information.
+# example options for ARP monitoring with three targets
+alias bond0 bonding
+options bond0 arp_interval=60 arp_ip_target=192.168.0.1,192.168.0.3,192.168.0.9
-7. Which switches/systems does it work with?
+ For just a single target the options would resemble:
- In round-robin and XOR mode, it works with systems that support
- trunking:
+# example options for ARP monitoring with one target
+alias bond0 bonding
+options bond0 arp_interval=60 arp_ip_target=192.168.0.100
- * Many Cisco switches and routers (look for EtherChannel support).
- * SunTrunking software.
- * Alteon AceDirector switches / WebOS (use Trunks).
- * BayStack Switches (trunks must be explicitly configured). Stackable
- models (450) can define trunks between ports on different physical
- units.
- * Linux bonding, of course !
- In 802.3ad mode, it works with with systems that support IEEE 802.3ad
- Dynamic Link Aggregation:
+8.3 MII Monitor Operation
+-------------------------
+
+ The MII monitor monitors only the carrier state of the local
+network interface. It accomplishes this in one of three ways: by
+depending upon the device driver to maintain its carrier state, by
+querying the device's MII registers, or by making an ethtool query to
+the device.
+
+ If the use_carrier module parameter is 1 (the default value),
+then the MII monitor will rely on the driver for carrier state
+information (via the netif_carrier subsystem). As explained in the
+use_carrier parameter information, above, if the MII monitor fails to
+detect carrier loss on the device (e.g., when the cable is physically
+disconnected), it may be that the driver does not support
+netif_carrier.
+
+ If use_carrier is 0, then the MII monitor will first query the
+device's (via ioctl) MII registers and check the link state. If that
+request fails (not just that it returns carrier down), then the MII
+monitor will make an ethtool ETHOOL_GLINK request to attempt to obtain
+the same information. If both methods fail (i.e., the driver either
+does not support or had some error in processing both the MII register
+and ethtool requests), then the MII monitor will assume the link is
+up.
+
+9. Potential Sources of Trouble
+===============================
+
+9.1 Adventures in Routing
+-------------------------
+
+ When bonding is configured, it is important that the slave
+devices not have routes that supercede routes of the master (or,
+generally, not have routes at all). For example, suppose the bonding
+device bond0 has two slaves, eth0 and eth1, and the routing table is
+as follows:
- * Extreme networks Summit 7i (look for link-aggregation).
- * Many Cisco switches and routers (look for LACP support; this may
- require an upgrade to your IOS software; LACP support was added
- by Cisco in late 2002).
- * Foundry Big Iron 4000
+Kernel IP routing table
+Destination Gateway Genmask Flags MSS Window irtt Iface
+10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth0
+10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth1
+10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 bond0
+127.0.0.0 0.0.0.0 255.0.0.0 U 40 0 0 lo
- In active-backup, balance-tlb and balance-alb modes, it should work
- with any Layer-II switch.
+ This routing configuration will likely still update the
+receive/transmit times in the driver (needed by the ARP monitor), but
+may bypass the bonding driver (because outgoing traffic to, in this
+case, another host on network 10 would use eth0 or eth1 before bond0).
+
+ The ARP monitor (and ARP itself) may become confused by this
+configuration, because ARP requests (generated by the ARP monitor)
+will be sent on one interface (bond0), but the corresponding reply
+will arrive on a different interface (eth0). This reply looks to ARP
+as an unsolicited ARP reply (because ARP matches replies on an
+interface basis), and is discarded. The MII monitor is not affected
+by the state of the routing table.
+
+ The solution here is simply to insure that slaves do not have
+routes of their own, and if for some reason they must, those routes do
+not supercede routes of their master. This should generally be the
+case, but unusual configurations or errant manual or automatic static
+route additions may cause trouble.
+
+9.2 Ethernet Device Renaming
+----------------------------
+ On systems with network configuration scripts that do not
+associate physical devices directly with network interface names (so
+that the same physical device always has the same "ethX" name), it may
+be necessary to add some special logic to either /etc/modules.conf or
+/etc/modprobe.conf (depending upon which is installed on the system).
-8. Where does a bonding device get its MAC address from?
+ For example, given a modules.conf containing the following:
- If not explicitly configured with ifconfig, the MAC address of the
- bonding device is taken from its first slave device. This MAC address
- is then passed to all following slaves and remains persistent (even if
- the the first slave is removed) until the bonding device is brought
- down or reconfigured.
+alias bond0 bonding
+options bond0 mode=some-mode miimon=50
+alias eth0 tg3
+alias eth1 tg3
+alias eth2 e1000
+alias eth3 e1000
+
+ If neither eth0 and eth1 are slaves to bond0, then when the
+bond0 interface comes up, the devices may end up reordered. This
+happens because bonding is loaded first, then its slave device's
+drivers are loaded next. Since no other drivers have been loaded,
+when the e1000 driver loads, it will receive eth0 and eth1 for its
+devices, but the bonding configuration tries to enslave eth2 and eth3
+(which may later be assigned to the tg3 devices).
+
+ Adding the following:
+
+add above bonding e1000 tg3
+
+ causes modprobe to load e1000 then tg3, in that order, when
+bonding is loaded. This command is fully documented in the
+modules.conf manual page.
+
+ On systems utilizing modprobe.conf (or modprobe.conf.local),
+an equivalent problem can occur. In this case, the following can be
+added to modprobe.conf (or modprobe.conf.local, as appropriate), as
+follows (all on one line; it has been split here for clarity):
+
+install bonding /sbin/modprobe tg3; /sbin/modprobe e1000;
+ /sbin/modprobe --ignore-install bonding
+
+ This will, when loading the bonding module, rather than
+performing the normal action, instead execute the provided command.
+This command loads the device drivers in the order needed, then calls
+modprobe with --ingore-install to cause the normal action to then take
+place. Full documentation on this can be found in the modprobe.conf
+and modprobe manual pages.
+
+9.3. Painfully Slow Or No Failed Link Detection By Miimon
+---------------------------------------------------------
+
+ By default, bonding enables the use_carrier option, which
+instructs bonding to trust the driver to maintain carrier state.
+
+ As discussed in the options section, above, some drivers do
+not support the netif_carrier_on/_off link state tracking system.
+With use_carrier enabled, bonding will always see these links as up,
+regardless of their actual state.
+
+ Additionally, other drivers do support netif_carrier, but do
+not maintain it in real time, e.g., only polling the link state at
+some fixed interval. In this case, miimon will detect failures, but
+only after some long period of time has expired. If it appears that
+miimon is very slow in detecting link failures, try specifying
+use_carrier=0 to see if that improves the failure detection time. If
+it does, then it may be that the driver checks the carrier state at a
+fixed interval, but does not cache the MII register values (so the
+use_carrier=0 method of querying the registers directly works). If
+use_carrier=0 does not improve the failover, then the driver may cache
+the registers, or the problem may be elsewhere.
+
+ Also, remember that miimon only checks for the device's
+carrier state. It has no way to determine the state of devices on or
+beyond other ports of a switch, or if a switch is refusing to pass
+traffic while still maintaining carrier on.
+
+10. SNMP agents
+===============
+
+ If running SNMP agents, the bonding driver should be loaded
+before any network drivers participating in a bond. This requirement
+is due to the the interface index (ipAdEntIfIndex) being associated to
+the first interface found with a given IP address. That is, there is
+only one ipAdEntIfIndex for each IP address. For example, if eth0 and
+eth1 are slaves of bond0 and the driver for eth0 is loaded before the
+bonding driver, the interface for the IP address will be associated
+with the eth0 interface. This configuration is shown below, the IP
+address 192.168.1.1 has an interface index of 2 which indexes to eth0
+in the ifDescr table (ifDescr.2).
- If you wish to change the MAC address, you can set it with ifconfig:
+ interfaces.ifTable.ifEntry.ifDescr.1 = lo
+ interfaces.ifTable.ifEntry.ifDescr.2 = eth0
+ interfaces.ifTable.ifEntry.ifDescr.3 = eth1
+ interfaces.ifTable.ifEntry.ifDescr.4 = eth2
+ interfaces.ifTable.ifEntry.ifDescr.5 = eth3
+ interfaces.ifTable.ifEntry.ifDescr.6 = bond0
+ ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.10.10.10 = 5
+ ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.1.1 = 2
+ ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.74.20.94 = 4
+ ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1
- # ifconfig bond0 hw ether 00:11:22:33:44:55
+ This problem is avoided by loading the bonding driver before
+any network drivers participating in a bond. Below is an example of
+loading the bonding driver first, the IP address 192.168.1.1 is
+correctly associated with ifDescr.2.
- The MAC address can be also changed by bringing down/up the device
- and then changing its slaves (or their order):
+ interfaces.ifTable.ifEntry.ifDescr.1 = lo
+ interfaces.ifTable.ifEntry.ifDescr.2 = bond0
+ interfaces.ifTable.ifEntry.ifDescr.3 = eth0
+ interfaces.ifTable.ifEntry.ifDescr.4 = eth1
+ interfaces.ifTable.ifEntry.ifDescr.5 = eth2
+ interfaces.ifTable.ifEntry.ifDescr.6 = eth3
+ ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.10.10.10 = 6
+ ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.1.1 = 2
+ ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.74.20.94 = 5
+ ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1
- # ifconfig bond0 down ; modprobe -r bonding
- # ifconfig bond0 .... up
- # ifenslave bond0 eth...
+ While some distributions may not report the interface name in
+ifDescr, the association between the IP address and IfIndex remains
+and SNMP functions such as Interface_Scan_Next will report that
+association.
- This method will automatically take the address from the next slave
- that will be added.
+11. Promiscuous mode
+====================
- To restore your slaves' MAC addresses, you need to detach them
- from the bond (`ifenslave -d bond0 eth0'). The bonding driver will then
- restore the MAC addresses that the slaves had before they were enslaved.
+ When running network monitoring tools, e.g., tcpdump, it is
+common to enable promiscuous mode on the device, so that all traffic
+is seen (instead of seeing only traffic destined for the local host).
+The bonding driver handles promiscuous mode changes to the bonding
+master device (e.g., bond0), and propogates the setting to the slave
+devices.
-9. Which transmit polices can be used?
+ For the balance-rr, balance-xor, broadcast, and 802.3ad modes,
+the promiscuous mode setting is propogated to all slaves.
- Round-robin, based on the order of enslaving, the output device
- is selected base on the next available slave. Regardless of
- the source and/or destination of the packet.
+ For the active-backup, balance-tlb and balance-alb modes, the
+promiscuous mode setting is propogated only to the active slave.
- Active-backup policy that ensures that one and only one device will
- transmit at any given moment. Active-backup policy is useful for
- implementing high availability solutions using two hubs (see
- section on High Availability).
+ For balance-tlb mode, the active slave is the slave currently
+receiving inbound traffic.
- XOR, based on (src hw addr XOR dst hw addr) % slave count. This
- policy selects the same slave for each destination hw address.
+ For balance-alb mode, the active slave is the slave used as a
+"primary." This slave is used for mode-specific control traffic, for
+sending to peers that are unassigned or if the load is unbalanced.
- Broadcast policy transmits everything on all slave interfaces.
+ For the active-backup, balance-tlb and balance-alb modes, when
+the active slave changes (e.g., due to a link failure), the
+promiscuous setting will be propogated to the new active slave.
- 802.3ad, based on XOR but distributes traffic among all interfaces
- in the active aggregator.
+12. High Availability Information
+=================================
- Transmit load balancing (balance-tlb) balances the traffic
- according to the current load on each slave. The balancing is
- clients based and the least loaded slave is selected for each new
- client. The load of each slave is calculated relative to its speed
- and enables load balancing in mixed speed teams.
+ High Availability refers to configurations that provide
+maximum network availability by having redundant or backup devices,
+links and switches between the host and the rest of the world.
- Adaptive load balancing (balance-alb) uses the Transmit load
- balancing for the transmit load. The receive load is balanced only
- among the group of highest speed active slaves in the bond. The
- load is distributed with round-robin i.e. next available slave in
- the high speed group of active slaves.
+ There are currently two basic methods for configuring to
+maximize availability. They are dependent on the network topology and
+the primary goal of the configuration, but in general, a configuration
+can be optimized for maximum available bandwidth, or for maximum
+network availability.
-High Availability
-=================
+12.1 High Availability in a Single Switch Topology
+--------------------------------------------------
-To implement high availability using the bonding driver, the driver needs to be
-compiled as a module, because currently it is the only way to pass parameters
-to the driver. This may change in the future.
+ If two hosts (or a host and a switch) are directly connected
+via multiple physical links, then there is no network availability
+penalty for optimizing for maximum bandwidth: there is only one switch
+(or peer), so if it fails, you have no alternative access to fail over
+to.
-High availability is achieved by using MII or ETHTOOL status reporting. You
-need to verify that all your interfaces support MII or ETHTOOL link status
-reporting. On Linux kernel 2.2.17, all the 100 Mbps capable drivers and
-yellowfin gigabit driver support MII. To determine if ETHTOOL link reporting
-is available for interface eth0, type "ethtool eth0" and the "Link detected:"
-line should contain the correct link status. If your system has an interface
-that does not support MII or ETHTOOL status reporting, a failure of its link
-will not be detected! A message indicating MII and ETHTOOL is not supported by
-a network driver is logged when the bonding driver is loaded with a non-zero
-miimon value.
+Example 1 : host to switch (or other host)
-The bonding driver can regularly check all its slaves links using the ETHTOOL
-IOCTL (ETHTOOL_GLINK command) or by checking the MII status registers. The
-check interval is specified by the module argument "miimon" (MII monitoring).
-It takes an integer that represents the checking time in milliseconds. It
-should not come to close to (1000/HZ) (10 milli-seconds on i386) because it
-may then reduce the system interactivity. A value of 100 seems to be a good
-starting point. It means that a dead link will be detected at most 100
-milli-seconds after it goes down.
+ +----------+ +----------+
+ | |eth0 eth0| switch |
+ | Host A +--------------------------+ or |
+ | +--------------------------+ other |
+ | |eth1 eth1| host |
+ +----------+ +----------+
-Example:
- # modprobe bonding miimon=100
+12.1.1 Bonding Mode Selection for single switch topology
+--------------------------------------------------------
+
+ This configuration is the easiest to set up and to understand,
+although you will have to decide which bonding mode best suits your
+needs. The tradeoffs for each mode are detailed below:
+
+balance-rr: This mode is the only mode that will permit a single
+ TCP/IP connection to stripe traffic across multiple
+ interfaces. It is therefore the only mode that will allow a
+ single TCP/IP stream to utilize more than one interface's
+ worth of throughput. This comes at a cost, however: the
+ striping often results in peer systems receiving packets out
+ of order, causing TCP/IP's congestion control system to kick
+ in, often by retransmitting segments.
+
+ It is possible to adjust TCP/IP's congestion limits by
+ altering the net.ipv4.tcp_reordering sysctl parameter. The
+ usual default value is 3, and the maximum useful value is 127.
+ For a four interface balance-rr bond, expect that a single
+ TCP/IP stream will utilize no more than approximately 2.3
+ interface's worth of throughput, even after adjusting
+ tcp_reordering.
+
+ If you are utilizing protocols other than TCP/IP, UDP for
+ example, and your application can tolerate out of order
+ delivery, then this mode can allow for single stream datagram
+ performance that scales near linearly as interfaces are added
+ to the bond.
+
+ This mode requires the switch to have the appropriate ports
+ configured for "etherchannel" or "trunking."
+
+active-backup: There is not much advantage in this network topology to
+ the active-backup mode, as the inactive backup devices are all
+ connected to the same peer as the primary. In this case, a
+ load balancing mode (with link monitoring) will provide the
+ same level of network availability, but with increased
+ available bandwidth. On the plus side, it does not require
+ any configuration of the switch.
+
+balance-xor: This mode will limit traffic such that packets destined
+ for specific peers will always be sent over the same
+ interface. Since the destination is determined by the MAC
+ addresses involved, this may be desirable if you have a large
+ network with many hosts. It is likely to be suboptimal if all
+ your traffic is passed through a single router, however. As
+ with balance-rr, the switch ports need to be configured for
+ "etherchannel" or "trunking."
+
+broadcast: Like active-backup, there is not much advantage to this
+ mode in this type of network topology.
+
+802.3ad: This mode can be a good choice for this type of network
+ topology. The 802.3ad mode is an IEEE standard, so all peers
+ that implement 802.3ad should interoperate well. The 802.3ad
+ protocol includes automatic configuration of the aggregates,
+ so minimal manual configuration of the switch is needed
+ (typically only to designate that some set of devices is
+ usable for 802.3ad). The 802.3ad standard also mandates that
+ frames be delivered in order (within certain limits), so in
+ general single connections will not see misordering of
+ packets. The 802.3ad mode does have some drawbacks: the
+ standard mandates that all devices in the aggregate operate at
+ the same speed and duplex. Also, as with all bonding load
+ balance modes other than balance-rr, no single connection will
+ be able to utilize more than a single interface's worth of
+ bandwidth. Additionally, the linux bonding 802.3ad
+ implementation distributes traffic by peer (using an XOR of
+ MAC addresses), so in general all traffic to a particular
+ destination will use the same interface. Finally, the 802.3ad
+ mode mandates the use of the MII monitor, therefore, the ARP
+ monitor is not available in this mode.
+
+balance-tlb: This mode is also a good choice for this type of
+ topology. It has no special switch configuration
+ requirements, and balances outgoing traffic by peer, in a
+ vaguely intelligent manner (not a simple XOR as in balance-xor
+ or 802.3ad mode), so that unlucky MAC addresses will not all
+ "bunch up" on a single interface. Interfaces may be of
+ differing speeds. On the down side, in this mode all incoming
+ traffic arrives over a single interface, this mode requires
+ certain ethtool support in the network device driver of the
+ slave interfaces, and the ARP monitor is not available.
+
+balance-alb: This mode is everything that balance-tlb is, and more. It
+ has all of the features (and restrictions) of balance-tlb, and
+ will also balance incoming traffic from peers (as described in
+ the Bonding Module Options section, above). The only extra
+ down side to this mode is that the network device driver must
+ support changing the hardware address while the device is
+ open.
+
+12.1.2 Link Monitoring for Single Switch Topology
+-------------------------------------------------
+
+ The choice of link monitoring may largely depend upon which
+mode you choose to use. The more advanced load balancing modes do not
+support the use of the ARP monitor, and are thus restricted to using
+the MII monitor (which does not provide as high a level of assurance
+as the ARP monitor).
+
+
+12.2 High Availability in a Multiple Switch Topology
+----------------------------------------------------
+
+ With multiple switches, the configuration of bonding and the
+network changes dramatically. In multiple switch topologies, there is
+a tradeoff between network availability and usable bandwidth.
+
+ Below is a sample network, configured to maximize the
+availability of the network:
-Or, put the following line in /etc/modprobe.conf:
+ | |
+ |port3 port3|
+ +-----+----+ +-----+----+
+ | |port2 ISL port2| |
+ | switch A +--------------------------+ switch B |
+ | | | |
+ +-----+----+ +-----++---+
+ |port1 port1|
+ | +-------+ |
+ +-------------+ host1 +---------------+
+ eth0 +-------+ eth1
- options bond0 miimon=100
+ In this configuration, there is a link between the two
+switches (ISL, or inter switch link), and multiple ports connecting to
+the outside world ("port3" on each switch). There is no technical
+reason that this could not be extended to a third switch.
+
+12.2.1 Bonding Mode Selection for Multiple Switch Topology
+----------------------------------------------------------
+
+ In a topology such as this, the active-backup and broadcast
+modes are the only useful bonding modes; the other modes require all
+links to terminate on the same peer for them to behave rationally.
+
+active-backup: This is generally the preferred mode, particularly if
+ the switches have an ISL and play together well. If the
+ network configuration is such that one switch is specifically
+ a backup switch (e.g., has lower capacity, higher cost, etc),
+ then the primary option can be used to insure that the
+ preferred link is always used when it is available.
+
+broadcast: This mode is really a special purpose mode, and is suitable
+ only for very specific needs. For example, if the two
+ switches are not connected (no ISL), and the networks beyond
+ them are totally independant. In this case, if it is
+ necessary for some specific one-way traffic to reach both
+ independent networks, then the broadcast mode may be suitable.
+
+12.2.2 Link Monitoring Selection for Multiple Switch Topology
+-------------------------------------------------------------
+
+ The choice of link monitoring ultimately depends upon your
+switch. If the switch can reliably fail ports in response to other
+failures, then either the MII or ARP monitors should work. For
+example, in the above example, if the "port3" link fails at the remote
+end, the MII monitor has no direct means to detect this. The ARP
+monitor could be configured with a target at the remote end of port3,
+thus detecting that failure without switch support.
+
+ In general, however, in a multiple switch topology, the ARP
+monitor can provide a higher level of reliability in detecting link
+failures. Additionally, it should be configured with multiple targets
+(at least one for each switch in the network). This will insure that,
+regardless of which switch is active, the ARP monitor has a suitable
+target to query.
+
+
+12.3 Switch Behavior Issues for High Availability
+-------------------------------------------------
+
+ You may encounter issues with the timing of link up and down
+reporting by the switch.
+
+ First, when a link comes up, some switches may indicate that
+the link is up (carrier available), but not pass traffic over the
+interface for some period of time. This delay is typically due to
+some type of autonegotiation or routing protocol, but may also occur
+during switch initialization (e.g., during recovery after a switch
+failure). If you find this to be a problem, specify an appropriate
+value to the updelay bonding module option to delay the use of the
+relevant interface(s).
+
+ Second, some switches may "bounce" the link state one or more
+times while a link is changing state. This occurs most commonly while
+the switch is initializing. Again, an appropriate updelay value may
+help, but note that if all links are down, then updelay is ignored
+when any link becomes active (the slave closest to completing its
+updelay is chosen).
+
+ Note that when a bonding interface has no active links, the
+driver will immediately reuse the first link that goes up, even if
+updelay parameter was specified. If there are slave interfaces
+waiting for the updelay timeout to expire, the interface that first
+went into that state will be immediately reused. This reduces down
+time of the network if the value of updelay has been overestimated.
+
+ In addition to the concerns about switch timings, if your
+switches take a long time to go into backup mode, it may be desirable
+to not activate a backup interface immediately after a link goes down.
+Failover may be delayed via the downdelay bonding module option.
+
+13. Hardware Specific Considerations
+====================================
+
+ This section contains additional information for configuring
+bonding on specific hardware platforms, or for interfacing bonding
+with particular switches or other devices.
+
+13.1 IBM BladeCenter
+--------------------
+
+ This applies to the JS20 and similar systems.
+
+ On the JS20 blades, the bonding driver supports only
+balance-rr, active-backup, balance-tlb and balance-alb modes. This is
+largely due to the network topology inside the BladeCenter, detailed
+below.
+
+JS20 network adapter information
+--------------------------------
+
+ All JS20s come with two Broadcom Gigabit Ethernet ports
+integrated on the planar. In the BladeCenter chassis, the eth0 port
+of all JS20 blades is hard wired to I/O Module #1; similarly, all eth1
+ports are wired to I/O Module #2. An add-on Broadcom daughter card
+can be installed on a JS20 to provide two more Gigabit Ethernet ports.
+These ports, eth2 and eth3, are wired to I/O Modules 3 and 4,
+respectively.
+
+ Each I/O Module may contain either a switch or a passthrough
+module (which allows ports to be directly connected to an external
+switch). Some bonding modes require a specific BladeCenter internal
+network topology in order to function; these are detailed below.
+
+ Additional BladeCenter-specific networking information can be
+found in two IBM Redbooks (www.ibm.com/redbooks):
+
+"IBM eServer BladeCenter Networking Options"
+"IBM eServer BladeCenter Layer 2-7 Network Switching"
+
+BladeCenter networking configuration
+------------------------------------
-There are currently two policies for high availability. They are dependent on
-whether:
+ Because a BladeCenter can be configured in a very large number
+of ways, this discussion will be confined to describing basic
+configurations.
+
+ Normally, Ethernet Switch Modules (ESM) are used in I/O
+modules 1 and 2. In this configuration, the eth0 and eth1 ports of a
+JS20 will be connected to different internal switches (in the
+respective I/O modules).
+
+ An optical passthru module (OPM) connects the I/O module
+directly to an external switch. By using OPMs in I/O module #1 and
+#2, the eth0 and eth1 interfaces of a JS20 can be redirected to the
+outside world and connected to a common external switch.
+
+ Depending upon the mix of ESM and OPM modules, the network
+will appear to bonding as either a single switch topology (all OPM
+modules) or as a multiple switch topology (one or more ESM modules,
+zero or more OPM modules). It is also possible to connect ESM modules
+together, resulting in a configuration much like the example in "High
+Availability in a multiple switch topology."
+
+Requirements for specifc modes
+------------------------------
+
+ The balance-rr mode requires the use of OPM modules for
+devices in the bond, all connected to an common external switch. That
+switch must be configured for "etherchannel" or "trunking" on the
+appropriate ports, as is usual for balance-rr.
+
+ The balance-alb and balance-tlb modes will function with
+either switch modules or passthrough modules (or a mix). The only
+specific requirement for these modes is that all network interfaces
+must be able to reach all destinations for traffic sent over the
+bonding device (i.e., the network must converge at some point outside
+the BladeCenter).
+
+ The active-backup mode has no additional requirements.
+
+Link monitoring issues
+----------------------
+
+ When an Ethernet Switch Module is in place, only the ARP
+monitor will reliably detect link loss to an external switch. This is
+nothing unusual, but examination of the BladeCenter cabinet would
+suggest that the "external" network ports are the ethernet ports for
+the system, when it fact there is a switch between these "external"
+ports and the devices on the JS20 system itself. The MII monitor is
+only able to detect link failures between the ESM and the JS20 system.
+
+ When a passthrough module is in place, the MII monitor does
+detect failures to the "external" port, which is then directly
+connected to the JS20 system.
+
+Other concerns
+--------------
+
+ The Serial Over LAN link is established over the primary
+ethernet (eth0) only, therefore, any loss of link to eth0 will result
+in losing your SoL connection. It will not fail over with other
+network traffic.
+
+ It may be desirable to disable spanning tree on the switch
+(either the internal Ethernet Switch Module, or an external switch) to
+avoid fail-over delays issues when using bonding.
+
+
+14. Frequently Asked Questions
+==============================
- a) hosts are connected to a single host or switch that support trunking
+1. Is it SMP safe?
- b) hosts are connected to several different switches or a single switch that
- does not support trunking
+ Yes. The old 2.0.xx channel bonding patch was not SMP safe.
+The new driver was designed to be SMP safe from the start.
+2. What type of cards will work with it?
-1) High Availability on a single switch or host - load balancing
-----------------------------------------------------------------
-It is the easiest to set up and to understand. Simply configure the
-remote equipment (host or switch) to aggregate traffic over several
-ports (Trunk, EtherChannel, etc.) and configure the bonding interfaces.
-If the module has been loaded with the proper MII option, it will work
-automatically. You can then try to remove and restore different links
-and see in your logs what the driver detects. When testing, you may
-encounter problems on some buggy switches that disable the trunk for a
-long time if all ports in a trunk go down. This is not Linux, but really
-the switch (reboot it to ensure).
+ Any Ethernet type cards (you can even mix cards - a Intel
+EtherExpress PRO/100 and a 3com 3c905b, for example). They need not
+be of the same speed.
-Example 1 : host to host at twice the speed
+3. How many bonding devices can I have?
- +----------+ +----------+
- | |eth0 eth0| |
- | Host A +--------------------------+ Host B |
- | +--------------------------+ |
- | |eth1 eth1| |
- +----------+ +----------+
+ There is no limit.
- On each host :
- # modprobe bonding miimon=100
- # ifconfig bond0 addr
- # ifenslave bond0 eth0 eth1
+4. How many slaves can a bonding device have?
-Example 2 : host to switch at twice the speed
+ This is limited only by the number of network interfaces Linux
+supports and/or the number of network cards you can place in your
+system.
- +----------+ +----------+
- | |eth0 port1| |
- | Host A +--------------------------+ switch |
- | +--------------------------+ |
- | |eth1 port2| |
- +----------+ +----------+
+5. What happens when a slave link dies?
- On host A : On the switch :
- # modprobe bonding miimon=100 # set up a trunk on port1
- # ifconfig bond0 addr and port2
- # ifenslave bond0 eth0 eth1
+ If link monitoring is enabled, then the failing device will be
+disabled. The active-backup mode will fail over to a backup link, and
+other modes will ignore the failed link. The link will continue to be
+monitored, and should it recover, it will rejoin the bond (in whatever
+manner is appropriate for the mode). See the section on High
+Availability for additional information.
+
+ Link monitoring can be enabled via either the miimon or
+arp_interval paramters (described in the module paramters section,
+above). In general, miimon monitors the carrier state as sensed by
+the underlying network device, and the arp monitor (arp_interval)
+monitors connectivity to another host on the local network.
+
+ If no link monitoring is configured, the bonding driver will
+be unable to detect link failures, and will assume that all links are
+always available. This will likely result in lost packets, and a
+resulting degredation of performance. The precise performance loss
+depends upon the bonding mode and network configuration.
+6. Can bonding be used for High Availability?
-2) High Availability on two or more switches (or a single switch without
- trunking support)
----------------------------------------------------------------------------
-This mode is more problematic because it relies on the fact that there
-are multiple ports and the host's MAC address should be visible on one
-port only to avoid confusing the switches.
+ Yes. See the section on High Availability for details.
-If you need to know which interface is the active one, and which ones are
-backup, use ifconfig. All backup interfaces have the NOARP flag set.
+7. Which switches/systems does it work with?
-To use this mode, pass "mode=1" to the module at load time :
+ The full answer to this depends upon the desired mode.
- # modprobe bonding miimon=100 mode=active-backup
+ In the basic balance modes (balance-rr and balance-xor), it
+works with any system that supports etherchannel (also called
+trunking). Most managed switches currently available have such
+support, and many unmananged switches as well.
- or:
+ The advanced balance modes (balance-tlb and balance-alb) do
+not have special switch requirements, but do need device drivers that
+support specific features (described in the appropriate section under
+module paramters, above).
- # modprobe bonding miimon=100 mode=1
+ In 802.3ad mode, it works with with systems that support IEEE
+802.3ad Dynamic Link Aggregation. Most managed and many unmanaged
+switches currently available support 802.3ad.
-Or, put in your /etc/modprobe.conf :
+ The active-backup mode should work with any Layer-II switch.
- options bond0 miimon=100 mode=active-backup
+8. Where does a bonding device get its MAC address from?
-Example 1: Using multiple host and multiple switches to build a "no single
-point of failure" solution.
+ If not explicitly configured with ifconfig, the MAC address of
+the bonding device is taken from its first slave device. This MAC
+address is then passed to all following slaves and remains persistent
+(even if the the first slave is removed) until the bonding device is
+brought down or reconfigured.
+ If you wish to change the MAC address, you can set it with
+ifconfig:
- | |
- |port3 port3|
- +-----+----+ +-----+----+
- | |port7 ISL port7| |
- | switch A +--------------------------+ switch B |
- | +--------------------------+ |
- | |port8 port8| |
- +----++----+ +-----++---+
- port2||port1 port1||port2
- || +-------+ ||
- |+-------------+ host1 +---------------+|
- | eth0 +-------+ eth1 |
- | |
- | +-------+ |
- +--------------+ host2 +----------------+
- eth0 +-------+ eth1
+# ifconfig bond0 hw ether 00:11:22:33:44:55
-In this configuration, there is an ISL - Inter Switch Link (could be a trunk),
-several servers (host1, host2 ...) attached to both switches each, and one or
-more ports to the outside world (port3...). One and only one slave on each host
-is active at a time, while all links are still monitored (the system can
-detect a failure of active and backup links).
+ The MAC address can be also changed by bringing down/up the
+device and then changing its slaves (or their order):
-Each time a host changes its active interface, it sticks to the new one until
-it goes down. In this example, the hosts are negligibly affected by the
-expiration time of the switches' forwarding tables.
+# ifconfig bond0 down ; modprobe -r bonding
+# ifconfig bond0 .... up
+# ifenslave bond0 eth...
-If host1 and host2 have the same functionality and are used in load balancing
-by another external mechanism, it is good to have host1's active interface
-connected to one switch and host2's to the other. Such system will survive
-a failure of a single host, cable, or switch. The worst thing that may happen
-in the case of a switch failure is that half of the hosts will be temporarily
-unreachable until the other switch expires its tables.
+ This method will automatically take the address from the next
+slave that is added.
-Example 2: Using multiple ethernet cards connected to a switch to configure
- NIC failover (switch is not required to support trunking).
+ To restore your slaves' MAC addresses, you need to detach them
+from the bond (`ifenslave -d bond0 eth0'). The bonding driver will
+then restore the MAC addresses that the slaves had before they were
+enslaved.
+15. Resources and Links
+=======================
- +----------+ +----------+
- | |eth0 port1| |
- | Host A +--------------------------+ switch |
- | +--------------------------+ |
- | |eth1 port2| |
- +----------+ +----------+
+The latest version of the bonding driver can be found in the latest
+version of the linux kernel, found on http://kernel.org
- On host A : On the switch :
- # modprobe bonding miimon=100 mode=1 # (optional) minimize the time
- # ifconfig bond0 addr # for table expiration
- # ifenslave bond0 eth0 eth1
+Discussions regarding the bonding driver take place primarily on the
+bonding-devel mailing list, hosted at sourceforge.net. If you have
+questions or problems, post them to the list.
-Each time the host changes its active interface, it sticks to the new one until
-it goes down. In this example, the host is strongly affected by the expiration
-time of the switch forwarding table.
+bonding-devel@lists.sourceforge.net
+https://lists.sourceforge.net/lists/listinfo/bonding-devel
-3) Adapting to your switches' timing
-------------------------------------
-If your switches take a long time to go into backup mode, it may be
-desirable not to activate a backup interface immediately after a link goes
-down. It is possible to delay the moment at which a link will be
-completely disabled by passing the module parameter "downdelay" (in
-milliseconds, must be a multiple of miimon).
-
-When a switch reboots, it is possible that its ports report "link up" status
-before they become usable. This could fool a bond device by causing it to
-use some ports that are not ready yet. It is possible to delay the moment at
-which an active link will be reused by passing the module parameter "updelay"
-(in milliseconds, must be a multiple of miimon).
-
-A similar situation can occur when a host re-negotiates a lost link with the
-switch (a case of cable replacement).
-
-A special case is when a bonding interface has lost all slave links. Then the
-driver will immediately reuse the first link that goes up, even if updelay
-parameter was specified. (If there are slave interfaces in the "updelay" state,
-the interface that first went into that state will be immediately reused.) This
-allows to reduce down-time if the value of updelay has been overestimated.
-
-Examples :
-
- # modprobe bonding miimon=100 mode=1 downdelay=2000 updelay=5000
- # modprobe bonding miimon=100 mode=balance-rr downdelay=0 updelay=5000
-
-
-Promiscuous Sniffing notes
-==========================
-
-If you wish to bond channels together for a network sniffing
-application --- you wish to run tcpdump, or ethereal, or an IDS like
-snort, with its input aggregated from multiple interfaces using the
-bonding driver --- then you need to handle the Promiscuous interface
-setting by hand. Specifically, when you "ifconfing bond0 up" you
-must add the promisc flag there; it will be propagated down to the
-slave interfaces at ifenslave time; a full example might look like:
-
- ifconfig bond0 promisc up
- for if in eth1 eth2 ...;do
- ifconfig $if up
- ifenslave bond0 $if
- done
- snort ... -i bond0 ...
-
-Ifenslave also wants to propagate addresses from interface to
-interface, appropriately for its design functions in HA and channel
-capacity aggregating; but it works fine for unnumbered interfaces;
-just ignore all the warnings it emits.
-
-
-8021q VLAN support
-==================
+There is also a project site on sourceforge.
-It is possible to configure VLAN devices over a bond interface using the 8021q
-driver. However, only packets coming from the 8021q driver and passing through
-bonding will be tagged by default. Self generated packets, like bonding's
-learning packets or ARP packets generated by either ALB mode or the ARP
-monitor mechanism, are tagged internally by bonding itself. As a result,
-bonding has to "learn" what VLAN IDs are configured on top of it, and it uses
-those IDs to tag self generated packets.
-
-For simplicity reasons, and to support the use of adapters that can do VLAN
-hardware acceleration offloding, the bonding interface declares itself as
-fully hardware offloaing capable, it gets the add_vid/kill_vid notifications
-to gather the necessary information, and it propagates those actions to the
-slaves.
-In case of mixed adapter types, hardware accelerated tagged packets that should
-go through an adapter that is not offloading capable are "un-accelerated" by the
-bonding driver so the VLAN tag sits in the regular location.
-
-VLAN interfaces *must* be added on top of a bonding interface only after
-enslaving at least one slave. This is because until the first slave is added the
-bonding interface has a HW address of 00:00:00:00:00:00, which will be copied by
-the VLAN interface when it is created.
-
-Notice that a problem would occur if all slaves are released from a bond that
-still has VLAN interfaces on top of it. When later coming to add new slaves, the
-bonding interface would get a HW address from the first slave, which might not
-match that of the VLAN interfaces. It is recommended that either all VLANs are
-removed and then re-added, or to manually set the bonding interface's HW
-address so it matches the VLAN's. (Note: changing a VLAN interface's HW address
-would set the underlying device -- i.e. the bonding interface -- to promiscouos
-mode, which might not be what you want).
-
-
-Limitations
-===========
-The main limitations are :
- - only the link status is monitored. If the switch on the other side is
- partially down (e.g. doesn't forward anymore, but the link is OK), the link
- won't be disabled. Another way to check for a dead link could be to count
- incoming frames on a heavily loaded host. This is not applicable to small
- servers, but may be useful when the front switches send multicast
- information on their links (e.g. VRRP), or even health-check the servers.
- Use the arp_interval/arp_ip_target parameters to count incoming/outgoing
- frames.
-
-
-
-Resources and Links
-===================
-
-Current development on this driver is posted to:
- - http://www.sourceforge.net/projects/bonding/
+http://www.sourceforge.net/projects/bonding
Donald Becker's Ethernet Drivers and diag programs may be found at :
- http://www.scyld.com/network/
-You will also find a lot of information regarding Ethernet, NWay, MII, etc. at
-www.scyld.com.
-
-Patches for 2.2 kernels are at Willy Tarreau's site :
- - http://wtarreau.free.fr/pub/bonding/
- - http://www-miaif.lip6.fr/~tarreau/pub/bonding/
-
-To get latest informations about Linux Kernel development, please consult
-the Linux Kernel Mailing List Archives at :
- http://www.ussg.iu.edu/hypermail/linux/kernel/
+You will also find a lot of information regarding Ethernet, NWay, MII,
+etc. at www.scyld.com.
-- END --
git://git.onelab.eu / linux-2.6.git / blobdiff