This bug was initially created as a copy of Bug #2218631 I am copying this bug because: We should follow up on the comment from the original bug: https://bugzilla.redhat.com/show_bug.cgi?id=2218631#c18 Specifically, we should disable LSP_OPTIONS_MCAST_FLOOD_REPORTS for ports created by ml2/ovn: https://github.com/openstack/neutron/blob/b92d133de66411b9444855cc97480891d7d7b7b2/neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/ovn_client.py#L369 The hope is that this will alleviate the size of action lists in table=38 of OVN (for the flows that handle mcast flooding), making it a potential work around for the OVS action list size limitation (tracked in the original bug). Description of problem: After creating close to 1220 VMs on a single compute, networking breaks for all of them and we see the following errors in the logs: Jun 29 17:20:57 compute00 kernel: openvswitch: netlink: Flow action size exceeds max 32768 Jun 29 17:20:57 compute00 kernel: openvswitch: netlink: Flow action size exceeds max 32768 Jun 29 17:20:59 compute00 kernel: openvswitch: netlink: Flow action size exceeds max 32768 Jun 29 17:20:59 compute00 kernel: openvswitch: netlink: Flow action size exceeds max 32768 Jun 29 17:21:00 compute00 kernel: openvswitch: netlink: Flow action size exceeds max 32768 Jun 29 17:21:07 compute00 kernel: openvswitch: netlink: Flow action size exceeds max 32768 Jun 29 17:21:07 compute00 kernel: openvswitch: netlink: Flow action size exceeds max 32768 Jun 29 17:21:07 compute00 kernel: openvswitch: netlink: Flow action size exceeds max 32768 Jun 29 17:21:07 compute00 kernel: openvswitch: netlink: Flow action size exceeds max 32768 Jun 29 17:21:08 compute00 kernel: openvswitch: netlink: Flow action size exceeds max 32768 Jun 29 17:21:08 compute00 kernel: openvswitch: netlink: Flow action size exceeds max 32768 Jun 29 17:21:08 compute00 kernel: openvswitch: netlink: Flow action size exceeds max 32768 Jun 29 17:21:13 compute00 kernel: openvswitch: netlink: Flow action size exceeds max 32768 Jun 29 17:21:13 compute00 kernel: openvswitch: netlink: Flow action size exceeds max 32768 Jun 29 17:21:14 compute00 kernel: openvswitch: netlink: Flow action size exceeds max 32768 Jun 29 17:21:14 compute00 kernel: openvswitch: netlink: Flow action size exceeds max 32768 Jun 29 17:21:15 compute00 kernel: openvswitch: netlink: Flow action size exceeds max 32768 Jun 29 17:21:15 compute00 kernel: openvswitch: netlink: Flow action size exceeds max 32768 Version-Release number of selected component (if applicable): RHOSP16.2.5 How reproducible: Always Steps to Reproduce: 1. Create close to 1220 VMs (at 1219 it should still work) 2. 3. Actual results: Global outage Expected results: Create 2000 vMs on a single compute Additional info: