The following section describe common problems that you might encounter after/during the installation of the OVN ML2 driver with Devstack and possible solutions to these problems.

Launching VM’s failure

Disable AppArmor

Using Ubuntu you might encounter libvirt permission errors when trying to create OVS ports after launching a VM (from the nova compute log). Disabling AppArmor might help with this problem, check out for instructions on how to disable it.

Multi-Node setup not working

Geneve kernel module not supported

By default OVN creates tunnels between compute nodes using the Geneve protocol. Older kernels (< 3.18) don’t support the Geneve module and hence tunneling can’t work. You can check it with this command ‘lsmod | grep openvswitch’ (geneve should show up in the result list)

For more information about which upstream Kernel version is required for support of each tunnel type, see the answer to ” Why do tunnels not work when using a kernel module other than the one packaged with Open vSwitch?” in the OVS FAQ.

MTU configuration

This problem is not unique to OVN but is amplified due to the possible larger size of geneve header compared to other common tunneling protocols (VXLAN). If you are using VM’s as compute nodes make sure that you either lower the MTU size on the virtual interface or enable fragmentation on it.