Using Open vSwitch without kernel support ========================================= Open vSwitch can operate, at a cost in performance, entirely in userspace, without assistance from a kernel module. This file explains how to install Open vSwitch in such a mode. The userspace-only mode of Open vSwitch is considered experimental. It has not been thoroughly tested. This version of Open vSwitch should be built manually with "configure" and "make". Debian packaging for Open vSwitch is also included, but it has not been recently tested, and so Debian packages are not a recommended way to use this version of Open vSwitch. Building and Installing ----------------------- The requirements and procedure for building, installing, and configuring Open vSwitch are the same as those given in INSTALL. You may omit configuring, building, and installing the kernel module, and the related requirements. On Linux, the userspace switch additionally requires the kernel TUN/TAP driver to be available, either built into the kernel or loaded as a module. If you are not sure, check for a directory named /sys/class/misc/tun. If it does not exist, then attempt to load the module with "modprobe tun". The tun device must also exist as /dev/net/tun. If it does not exist, then create /dev/net (if necessary) with "mkdir /dev/net", then create /dev/net/tun with "mknod /dev/net/tun c 10 200". On FreeBSD, the userspace switch additionally requires the kernel tap(4) driver to be available, either built into the kernel or loaded as a module. Using the Userspace Datapath with ovs-vswitchd ---------------------------------------------- To use ovs-vswitchd in userspace mode, create a bridge with datapath_type "netdev" in the configuration database. For example: ovs-vsctl add-br br0 ovs-vsctl set bridge br0 datapath_type=netdev ovs-vsctl add-port br0 eth0 ovs-vsctl add-port br0 eth1 ovs-vsctl add-port br0 eth2 ovs-vswitchd will create a TAP device as the bridge's local interface, named the same as the bridge, as well as for each configured internal interface. Firewall Rules -------------- On Linux, when a physical interface is in use by the userspace datapath, packets received on the interface still also pass into the kernel TCP/IP stack. This can cause surprising and incorrect behavior. You can use "iptables" to avoid this behavior, by using it to drop received packets. For example, to drop packets received on eth0: iptables -A INPUT -i eth0 -j DROP iptables -A FORWARD -i eth0 -j DROP Bug Reporting ------------- Please report problems to bugs@openvswitch.org.