X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=FAQ;h=72a147978b7b4b3d2398700f83f28ba7394cfe13;hb=eb857b4824d2a62e1cc1b85c30a3da007d4942c9;hp=a6dd56825d537ebaa7df82d925b9d3ac326f127b;hpb=5cb2356b599a1697825419cf4b7dda81ff07d517;p=sliver-openvswitch.git diff --git a/FAQ b/FAQ index a6dd56825..72a147978 100644 --- a/FAQ +++ b/FAQ @@ -128,27 +128,43 @@ A: All official releases have been through a comprehensive testing supplanted by the next major release. The current LTS release is 1.4.x. +Q: What Linux kernel versions does each Open vSwitch release work with? + +A: The following table lists the Linux kernel versions against which the + given versions of the Open vSwitch kernel module will successfully + build. The Linux kernel versions are upstream kernel versions, so + Linux kernels modified from the upstream sources may not build in + some cases even if they are based on a supported version. This is + most notably true of Red Hat Enterprise Linux (RHEL) kernels, which + are extensively modified from upstream. + + Open vSwitch Linux kernel + ------------ ------------- + 1.4.x 2.6.18 to 3.2 + 1.5.x 2.6.18 to 3.2 + 1.6.x 2.6.18 to 3.2 + 1.7.x 2.6.18 to 3.3 + 1.8.x 2.6.18 to 3.4 + 1.9.x 2.6.18 to 3.8 + + Open vSwitch userspace should also work with the Linux kernel module + built into Linux 3.3 and later. + + Open vSwitch userspace is not sensitive to the Linux kernel version. + It should build against almost any kernel, certainly against 2.6.18 + and later. + Q: What features are not available in the Open vSwitch kernel datapath that ships as part of the upstream Linux kernel? A: The kernel module in upstream Linux 3.3 and later does not include the following features: - - Bridge compatibility, that is, support for the ovs-brcompatd - daemon that (if you enable it) lets "brctl" and other Linux - bridge tools transparently work with Open vSwitch instead. - - We do not expect bridge compatibility to ever be available in - upstream Linux. If you need bridge compatibility, use the - kernel module from the Open vSwitch distribution instead of the - upstream Linux kernel module. - - - Tunnel and patch virtual ports, that is, interfaces with type - "gre", "ipsec_gre", "capwap", or "patch". It is possible to - create tunnels in Linux and attach them to Open vSwitch as - system devices. However, they cannot be dynamically created - through the OVSDB protocol or set the tunnel ids as a flow - action. + - Tunnel virtual ports, that is, interfaces with type "gre", + "ipsec_gre", "capwap". It is possible to create tunnels in + Linux and attach them to Open vSwitch as system devices. + However, they cannot be dynamically created through the OVSDB + protocol or set the tunnel ids as a flow action. Work is in progress in adding these features to the upstream Linux version of the Open vSwitch kernel module. For now, if @@ -156,6 +172,11 @@ A: The kernel module in upstream Linux 3.3 and later does not include vSwitch distribution instead of the upstream Linux kernel module. + - Patch virtual ports, that is, interfaces with type "patch". + You can use Linux "veth" devices as a substitute. + + We don't have any plans to add patch ports upstream. + Q: What features are not available when using the userspace datapath? A: Tunnel and patch virtual ports are not supported, as described in the @@ -164,6 +185,137 @@ A: Tunnel and patch virtual ports are not supported, as described in the may not be transmitted. +Terminology +----------- + +Q: I thought Open vSwitch was a virtual Ethernet switch, but the + documentation keeps talking about bridges. What's a bridge? + +A: In networking, the terms "bridge" and "switch" are synonyms. Open + vSwitch implements an Ethernet switch, which means that it is also + an Ethernet bridge. + +Q: What's a VLAN? + +A: See the "VLAN" section below. + + +Basic Configuration +------------------- + +Q: How do I configure a port as an access port? + +A: Add "tag=VLAN" to your "ovs-vsctl add-port" command. For example, + the following commands configure br0 with eth0 as a trunk port (the + default) and tap0 as an access port for VLAN 9: + + ovs-vsctl add-br br0 + ovs-vsctl add-port br0 eth0 + ovs-vsctl add-port br0 tap0 tag=9 + + If you want to configure an already added port as an access port, + use "ovs-vsctl set", e.g.: + + ovs-vsctl set port tap0 tag=9 + +Q: How do I configure a port as a SPAN port, that is, enable mirroring + of all traffic to that port? + +A: The following commands configure br0 with eth0 and tap0 as trunk + ports. All traffic coming in or going out on eth0 or tap0 is also + mirrored to tap1; any traffic arriving on tap1 is dropped: + + ovs-vsctl add-br br0 + ovs-vsctl add-port br0 eth0 + ovs-vsctl add-port br0 tap0 + ovs-vsctl add-port br0 tap1 \ + -- --id=@p get port tap1 \ + -- --id=@m create mirror name=m0 select-all=true output-port=@p \ + -- set bridge br0 mirrors=@m + + To later disable mirroring, run: + + ovs-vsctl clear bridge br0 mirrors + +Q: How do I configure a VLAN as an RSPAN VLAN, that is, enable + mirroring of all traffic to that VLAN? + +A: The following commands configure br0 with eth0 as a trunk port and + tap0 as an access port for VLAN 10. All traffic coming in or going + out on tap0, as well as traffic coming in or going out on eth0 in + VLAN 10, is also mirrored to VLAN 15 on eth0. The original tag for + VLAN 10, in cases where one is present, is dropped as part of + mirroring: + + ovs-vsctl add-br br0 + ovs-vsctl add-port br0 eth0 + ovs-vsctl add-port br0 tap0 tag=10 + ovs-vsctl \ + -- --id=@m create mirror name=m0 select-all=true select-vlan=10 \ + output-vlan=15 \ + -- set bridge br0 mirrors=@m + + To later disable mirroring, run: + + ovs-vsctl clear bridge br0 mirrors + + Mirroring to a VLAN can disrupt a network that contains unmanaged + switches. See ovs-vswitchd.conf.db(5) for details. Mirroring to a + GRE tunnel has fewer caveats than mirroring to a VLAN and should + generally be preferred. + +Q: Can I mirror more than one input VLAN to an RSPAN VLAN? + +A: Yes, but mirroring to a VLAN strips the original VLAN tag in favor + of the specified output-vlan. This loss of information may make + the mirrored traffic too hard to interpret. + + To mirror multiple VLANs, use the commands above, but specify a + comma-separated list of VLANs as the value for select-vlan. To + mirror every VLAN, use the commands above, but omit select-vlan and + its value entirely. + + When a packet arrives on a VLAN that is used as a mirror output + VLAN, the mirror is disregarded. Instead, in standalone mode, OVS + floods the packet across all the ports for which the mirror output + VLAN is configured. (If an OpenFlow controller is in use, then it + can override this behavior through the flow table.) If OVS is used + as an intermediate switch, rather than an edge switch, this ensures + that the RSPAN traffic is distributed through the network. + + Mirroring to a VLAN can disrupt a network that contains unmanaged + switches. See ovs-vswitchd.conf.db(5) for details. Mirroring to a + GRE tunnel has fewer caveats than mirroring to a VLAN and should + generally be preferred. + +Q: How do I configure mirroring of all traffic to a GRE tunnel? + +A: The following commands configure br0 with eth0 and tap0 as trunk + ports. All traffic coming in or going out on eth0 or tap0 is also + mirrored to gre0, a GRE tunnel to the remote host 192.168.1.10; any + traffic arriving on gre0 is dropped: + + ovs-vsctl add-br br0 + ovs-vsctl add-port br0 eth0 + ovs-vsctl add-port br0 tap0 + ovs-vsctl add-port br0 gre0 \ + -- set interface gre0 type=gre options:remote_ip=192.168.1.10 \ + -- --id=@p get port gre0 \ + -- --id=@m create mirror name=m0 select-all=true output-port=@p \ + -- set bridge br0 mirrors=@m + + To later disable mirroring and destroy the GRE tunnel: + + ovs-vsctl clear bridge br0 mirrors + ovs-vcstl del-port br0 gre0 + +Q: Does Open vSwitch support ERSPAN? + +A: No. ERSPAN is an undocumented proprietary protocol. As an + alternative, Open vSwitch supports mirroring to a GRE tunnel (see + above). + + Configuration Problems ---------------------- @@ -294,10 +446,176 @@ Q: Is there any documentation on the database tables and fields? A: Yes. ovs-vswitchd.conf.db(5) is a comprehensive reference. +Q: When I run ovs-dpctl I no longer see the bridges I created. Instead, + I only see a datapath called "ovs-system". How can I see datapath + information about a particular bridge? + +A: In version 1.9.0, OVS switched to using a single datapath that is + shared by all bridges of that type. The "ovs-appctl dpif/*" + commands provide similar functionality that is scoped by the bridge. + + +Quality of Service (QoS) +------------------------ + +Q: How do I configure Quality of Service (QoS)? + +A: Suppose that you want to set up bridge br0 connected to physical + Ethernet port eth0 (a 1 Gbps device) and virtual machine interfaces + vif1.0 and vif2.0, and that you want to limit traffic from vif1.0 + to eth0 to 10 Mbps and from vif2.0 to eth0 to 20 Mbps. Then, you + could configure the bridge this way: + + ovs-vsctl -- \ + add-br br0 -- \ + add-port br0 eth0 -- \ + add-port br0 vif1.0 -- set interface vif1.0 ofport_request=5 -- \ + add-port br0 vif2.0 -- set interface vif2.0 ofport_request=6 -- \ + set port eth0 qos=@newqos -- \ + --id=@newqos create qos type=linux-htb \ + other-config:max-rate=1000000000 \ + queues:123=@vif10queue \ + queues:234=@vif20queue -- \ + --id=@vif10queue create queue other-config:max-rate=10000000 -- \ + --id=@vif20queue create queue other-config:max-rate=20000000 + + At this point, bridge br0 is configured with the ports and eth0 is + configured with the queues that you need for QoS, but nothing is + actually directing packets from vif1.0 or vif2.0 to the queues that + we have set up for them. That means that all of the packets to + eth0 are going to the "default queue", which is not what we want. + + We use OpenFlow to direct packets from vif1.0 and vif2.0 to the + queues reserved for them: + + ovs-ofctl add-flow br0 in_port=5,actions=set_queue:123,normal + ovs-ofctl add-flow br0 in_port=6,actions=set_queue:234,normal + + Each of the above flows matches on the input port, sets up the + appropriate queue (123 for vif1.0, 234 for vif2.0), and then + executes the "normal" action, which performs the same switching + that Open vSwitch would have done without any OpenFlow flows being + present. (We know that vif1.0 and vif2.0 have OpenFlow port + numbers 5 and 6, respectively, because we set their ofport_request + columns above. If we had not done that, then we would have needed + to find out their port numbers before setting up these flows.) + + Now traffic going from vif1.0 or vif2.0 to eth0 should be + rate-limited. + + By the way, if you delete the bridge created by the above commands, + with: + + ovs-vsctl del-br br0 + + then that will leave one unreferenced QoS record and two + unreferenced Queue records in the Open vSwich database. One way to + clear them out, assuming you don't have other QoS or Queue records + that you want to keep, is: + + ovs-vsctl -- --all destroy QoS -- --all destroy Queue + +Q: I configured Quality of Service (QoS) in my OpenFlow network by + adding records to the QoS and Queue table, but the results aren't + what I expect. + +A: Did you install OpenFlow flows that use your queues? This is the + primary way to tell Open vSwitch which queues you want to use. If + you don't do this, then the default queue will be used, which will + probably not have the effect you want. + + Refer to the previous question for an example. + +Q: I configured QoS, correctly, but my measurements show that it isn't + working as well as I expect. + +A: With the Linux kernel, the Open vSwitch implementation of QoS has + two aspects: + + - Open vSwitch configures a subset of Linux kernel QoS + features, according to what is in OVSDB. It is possible that + this code has bugs. If you believe that this is so, then you + can configure the Linux traffic control (QoS) stack directly + with the "tc" program. If you get better results that way, + you can send a detailed bug report to bugs@openvswitch.org. + + It is certain that Open vSwitch cannot configure every Linux + kernel QoS feature. If you need some feature that OVS cannot + configure, then you can also use "tc" directly (or add that + feature to OVS). + + - The Open vSwitch implementation of OpenFlow allows flows to + be directed to particular queues. This is pretty simple and + unlikely to have serious bugs at this point. + + However, most problems with QoS on Linux are not bugs in Open + vSwitch at all. They tend to be either configuration errors + (please see the earlier questions in this section) or issues with + the traffic control (QoS) stack in Linux. The Open vSwitch + developers are not experts on Linux traffic control. We suggest + that, if you believe you are encountering a problem with Linux + traffic control, that you consult the tc manpages (e.g. tc(8), + tc-htb(8), tc-hfsc(8)), web resources (e.g. http://lartc.org/), or + mailing lists (e.g. http://vger.kernel.org/vger-lists.html#netdev). + VLANs ----- +Q: What's a VLAN? + +A: At the simplest level, a VLAN (short for "virtual LAN") is a way to + partition a single switch into multiple switches. Suppose, for + example, that you have two groups of machines, group A and group B. + You want the machines in group A to be able to talk to each other, + and you want the machine in group B to be able to talk to each + other, but you don't want the machines in group A to be able to + talk to the machines in group B. You can do this with two + switches, by plugging the machines in group A into one switch and + the machines in group B into the other switch. + + If you only have one switch, then you can use VLANs to do the same + thing, by configuring the ports for machines in group A as VLAN + "access ports" for one VLAN and the ports for group B as "access + ports" for a different VLAN. The switch will only forward packets + between ports that are assigned to the same VLAN, so this + effectively subdivides your single switch into two independent + switches, one for each group of machines. + + So far we haven't said anything about VLAN headers. With access + ports, like we've described so far, no VLAN header is present in + the Ethernet frame. This means that the machines (or switches) + connected to access ports need not be aware that VLANs are + involved, just like in the case where we use two different physical + switches. + + Now suppose that you have a whole bunch of switches in your + network, instead of just one, and that some machines in group A are + connected directly to both switches 1 and 2. To allow these + machines to talk to each other, you could add an access port for + group A's VLAN to switch 1 and another to switch 2, and then + connect an Ethernet cable between those ports. That works fine, + but it doesn't scale well as the number of switches and the number + of VLANs increases, because you use up a lot of valuable switch + ports just connecting together your VLANs. + + This is where VLAN headers come in. Instead of using one cable and + two ports per VLAN to connect a pair of switches, we configure a + port on each switch as a VLAN "trunk port". Packets sent and + received on a trunk port carry a VLAN header that says what VLAN + the packet belongs to, so that only two ports total are required to + connect the switches, regardless of the number of VLANs in use. + Normally, only switches (either physical or virtual) are connected + to a trunk port, not individual hosts, because individual hosts + don't expect to see a VLAN header in the traffic that they receive. + + None of the above discussion says anything about particular VLAN + numbers. This is because VLAN numbers are completely arbitrary. + One must only ensure that a given VLAN is numbered consistently + throughout a network and that different VLANs are given different + numbers. (That said, VLAN 0 is usually synonymous with a packet + that has no VLAN header, and VLAN 4095 is reserved.) + Q: VLANs don't work. A: Many drivers in Linux kernels before version 3.3 had VLAN-related @@ -372,6 +690,25 @@ A: It's possible that you have the VLAN configured on your physical equally well. Refer to the documentation for the Port table in ovs-vswitchd.conf.db(5) for more information. +Q: I added a pair of VMs on different VLANs, like this: + + ovs-vsctl add-br br0 + ovs-vsctl add-port br0 eth0 + ovs-vsctl add-port br0 tap0 tag=9 + ovs-vsctl add-port br0 tap1 tag=10 + + but the VMs can't access each other, the external network, or the + Internet. + +A: It is to be expected that the VMs can't access each other. VLANs + are a means to partition a network. When you configured tap0 and + tap1 as access ports for different VLANs, you indicated that they + should be isolated from each other. + + As for the external network and the Internet, it seems likely that + the machines you are trying to access are not on VLAN 9 (or 10) and + that the Internet is not available on VLAN 9 (or 10). + Q: Can I configure an IP address on a VLAN? A: Yes. Use an "internal port" configured as an access port. For @@ -404,18 +741,48 @@ A: The configuration for VLANs in the Open vSwitch database (e.g. via controller. This will only be suitable for some situations, though. +Q: I configured ports on a bridge as access ports with different VLAN + tags, like this: + + ovs-vsctl add-br br0 + ovs-vsctl set-controller br0 tcp:192.168.0.10:6633 + ovs-vsctl add-port br0 eth0 + ovs-vsctl add-port br0 tap0 tag=9 + ovs-vsctl add-port br0 tap1 tag=10 + + but the VMs running behind tap0 and tap1 can still communicate, + that is, they are not isolated from each other even though they are + on different VLANs. + +A: Do you have a controller configured on br0 (as the commands above + do)? If so, then this is a variant on the previous question, "My + OpenFlow controller doesn't see the VLANs that I expect," and you + can refer to the answer there for more information. + Controllers ----------- Q: What versions of OpenFlow does Open vSwitch support? -A: Open vSwitch supports OpenFlow 1.0. It also includes a number of - extensions that bring many of the features from later versions of - OpenFlow. Work is underway to provide support for later versions and - can be tracked here: +A: Open vSwitch 1.9 and earlier support only OpenFlow 1.0 (plus + extensions that bring in many of the features from later versions + of OpenFlow). + + Open vSwitch versions 1.10 and later will have experimental support + for OpenFlow 1.2 and 1.3. On these versions of Open vSwitch, the + following command enables OpenFlow 1.0, 1.2, and 1.3 on bridge br0: + + ovs-vsctl set bridge br0 protocols=openflow10,openflow12,openflow13 + + Support for OpenFlow 1.1 is incomplete enough that it cannot yet be + enabled, even experimentally. - http://openvswitch.org/development/openflow-1-x-plan/ + Support for OpenFlow 1.2 and 1.3 is still incomplete. Work to be + done is tracked in OPENFLOW-1.1+ in the Open vSwitch source tree + (also via http://openvswitch.org/development/openflow-1-x-plan/). + When support for a given OpenFlow version is solidly implemented, + Open vSwitch will enable that version by default. Q: I'm getting "error type 45250 code 0". What's that? @@ -520,6 +887,61 @@ A: The term "normalization" in the log message means that a flow TCP source port 1234, write "tcp,tp_src=1234", or to match UDP source port 1234, write "udp,tp_src=1234". +Q: How can I figure out the OpenFlow port number for a given port? + +A: The OFPT_FEATURES_REQUEST message requests an OpenFlow switch to + respond with an OFPT_FEATURES_REPLY that, among other information, + includes a mapping between OpenFlow port names and numbers. From a + command prompt, "ovs-ofctl show br0" makes such a request and + prints the response for switch br0. + + The Interface table in the Open vSwitch database also maps OpenFlow + port names to numbers. To print the OpenFlow port number + associated with interface eth0, run: + + ovs-vsctl get Interface eth0 ofport + + You can print the entire mapping with: + + ovs-vsctl -- --columns=name,ofport list Interface + + but the output mixes together interfaces from all bridges in the + database, so it may be confusing if more than one bridge exists. + + In the Open vSwitch database, ofport value -1 means that the + interface could not be created due to an error. (The Open vSwitch + log should indicate the reason.) ofport value [] (the empty set) + means that the interface hasn't been created yet. The latter is + normally an intermittent condition (unless ovs-vswitchd is not + running). + +Q: I added some flows with my controller or with ovs-ofctl, but when I + run "ovs-dpctl dump-flows" I don't see them. + +A: ovs-dpctl queries a kernel datapath, not an OpenFlow switch. It + won't display the information that you want. You want to use + "ovs-ofctl dump-flows" instead. + +Q: It looks like each of the interfaces in my bonded port shows up + as an individual OpenFlow port. Is that right? + +A: Yes, Open vSwitch makes individual bond interfaces visible as + OpenFlow ports, rather than the bond as a whole. The interfaces + are treated together as a bond for only a few purposes: + + - Sending a packet to the OFPP_NORMAL port. (When an OpenFlow + controller is not configured, this happens implicitly to + every packet.) + + - The "autopath" Nicira extension action. However, "autopath" + is deprecated and scheduled for removal in February 2013. + + - Mirrors configured for output to a bonded port. + + It would make a lot of sense for Open vSwitch to present a bond as + a single OpenFlow port. If you want to contribute an + implementation of such a feature, please bring it up on the Open + vSwitch development mailing list at dev@openvswitch.org. Contact -------