Comment 4 for bug 1913621

I am hitting an issue that is related to this and might help you to know about.

I do:
  * ussuri with dvr_snat
  * create port P1 with address A1 and create vm on node C1 with this port
  * associate floating ip with P1 and ping it
  * observe REACHABLE arp entry for A1 in qrouter arp cache
  * so far so good
  * restart the neutron-l3-agent
  * observe REACHABLE arp entry for A1 is now PERMANENT
  * delete vm and port
  * create port P2 with address A1 and create vm on node C1 with this port
  * vm is unreachable since arp cache contains wrong mac address of old port P1

So for me the issue is that if you restart the l3-agent it *does* set arp entries to PERMANENT for bound ports but it never deletes then so if you reuse ip addresses with new ports you will eventually not be able to reach them.