Description of problem:

After live migrating a VM instance, customer loses connectivity to the external port as well as the internal network ports to the VM instance. Workaround is to live-migrate it back to the original source but if that does not help (which happens sometimes), customer needs to detach and remove the external port from the VM instance and create and attach fresh external port to the VM instance. The external port of the affected VM instance is directly from the Neutron external network. The live migration activity also triggers the same connectivity problems with the other VM instances already residing on the destination node.

Version-Release number of selected component (if applicable):
FFUed from RHOSP 16.2 to RHOSP 17.1.2

How reproducible:

Not reproducible in other than the affected stack, CU tried to setup test on similar stack but can only trigger the issue on this stack

Steps to Reproduce:

Please see customer portal case collab request comment #80

Actual results:

Live migrated VM instance and instances already residing on the destination host lose connectivity.

Expected results:

Live migration of instance without loss of connectivity

Additional info:

This was tested again in a maintenance window together with support, a detailed description can be found in the customer portal case collab request comment #80
Packet captures, sosreports and other information are attached to the customer portal case

It is very hard to obtain a maintenance window for this issue, which takes several weeks and has huge monetary impact on the end customer because of loss of connectivity. Therefor it is very hard to test possible solutions hence why this BZ was opened.