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[Alan Pevec <1453855@xxxxxxxxxxxxxxxxxx>]

** Changed in: neutron/juno
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1453855

Title:
  HA routers may fail to send out GARPs when node boots

Status in neutron:
  Fix Released
Status in neutron juno series:
  Fix Released

Bug description:
  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 start 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

  These will be configurable and have sane defaults.

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