[j-nsp] vpls loop avoidance

[David Ball]

On 20 October 2011 14:00, William Cooper <wcooper02 at gmail.com> wrote:
> I might be confused... but wouldn't the switches learn the MAC to port
> association dynamically based
> on traffic flows?

 In the absence of gratuitous ARP (used, for example, by VRRP), no.
The switch will learn it once, cache it, and that MAC-to-port entry
will remain until it times out and is relearned (unless the switch
port goes down, in which case the switch will flush MACs learned on
that port).  This is where an earlier poster's idea of shortening the
MAC aging timeout on the switch could help a little, though some folks
might prefer faster failover than is afforded by MAC timeouts on a
dead (yet still admin/oper UP) port.  You can typically flush the MAC
table manually on the switch, but that's certainly not a viable
solution for speeding up automated failover.

David