OSPF slow reconvergence

Hello,

Just curious if anyone can shed some light on this. If you have OSPF hello
and dead timers set to 1 and 4 respectively, shouldn't OSPF reconverge
within 4 seconds of the loss of a neighbor? When I look at the routing
debugs in Dynamips it takes 6 seconds from the notification of OSPF being
down until the alternate route is added into the table.

I have a real world scenario where we are peering Cisco ASA firewalls with
Nortel ERS 8600 switches. The lowest the Nortel / Avaya engineers will
allow us to go down to is 1 and 4. The switches do not have millisecond
timers anyway so the lowest possible is 1 and 2. It's taking close to 10
seconds in that case which is not a good thing for VOIP.

Just wondering if this is the expected behavior for OSPF. The Avaya
engineers don't think so but testing in Dynamips seems to confirm it is.

Thanks,
Matt

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Received on Fri Apr 29 2011 - 10:00:27 ART