[ovs-dev] [PATCH v1 2/2] ovn: Send garp on localnet

Ben Pfaff blp at ovn.org
Tue Apr 12 16:26:10 UTC 2016


On Tue, Apr 12, 2016 at 12:58:44PM +0300, Vasiliy Tolstov wrote:
> 2016-04-12 4:29 GMT+03:00 Ben Pfaff <blp at ovn.org>:
> >> In some usecases such as VM migration or when VMs reuse IP addresses,
> >> VMs become unreachable externally because
> >> external switches/routers on localnet
> >> have stale port-mac or arp caches. The problem resolves
> >> after some time when the caches ageout which could be
> >> minutes for port-mac bindings or hours for arp caches.
> >>
> >> To fix this, send some gratuitous ARPs when a logical
> >> port on a localnet datapath gets added. Such gratuitous arps
> >> help on a best-effort basis to update the mac-port bindings and arp-caches
> >> of external switches and routers on the localnet.
> 
> Why send garp and not to create two flows that duplicates all traffic
> to source and destination vm?
> So in this case we don't need garp at all.

localnet is used for connecting to physical networks that OVN does not
control, so there is no way to do this.



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