Hi OpenStack Community,

I’ve indicated very weird behavior about ovn flows when VM is associated with vrouter, I use one new compute node with only 1 VM for testing and result as below:

• When VM attach to vRouter without external network: Only add new 2047 flows.
• When vRouter attach to external network (provider-net2): It will generate 147k flows immediately ?
• We’ve tested with VM direct attach to provider-net2 also generate 147k flows.

My environment is OpenStack Victoria version, neutron deployed with OVN, DVR, Distributed FIP mode, and provider-net2 using VLAN setup. The problems lead to the heavily process of sync flow which slows down the normal VM operations and packet drop a little bit while update large flow on the ovswitch.

Could anyone has experienced this behavior before or have a solution config/patch neutron to address this?  Any suggestions are highly appreciated.

Thank and regards,

Sang Tran