Comment 0 for bug 1453855

When a node boots, it starts the OVS and L3 agents. As an example, in RDO systemd unit files, these services have no dependency. This means that the L3 agent can stop before the OVS agent. It can start configuring routers before the OVS agent finished syncing with the server and starts processing ovsdb monitor updates. The result is that when the L3 agent finishes configuring an HA router, it starts up keepalived, which under certain conditions will transition to master and send our gratuitous ARPs before the OVS agent finishes plugging its ports. This means that the gratuitous ARP will be lost, but with the router acting as master, this can cause black holes.

Possible solutions:
* Introduce systemd dependencies, but this has its set of intricacies and it's hard to solve the above problem comprehensively just with this approach.
* Regardless, it's a good idea to use new keepalived flags:
garp_master_repeat <INTEGER> # how often the gratuitous ARP after MASTER
                                                                       # state transition should be repeated?
garp_master_refresh <INTEGER> # Periodic delay in seconds sending
                                                                       # gratuitous ARP while in MASTER state