From: dszarmach (dszarmach@comhs.org)
Date: Wed Mar 15 2006 - 01:19:49 GMT-3
to make things worse, the elections are separate, and the BDR always takes
over as DR upon DR failure
so if you have routers A,B,C
assume base config and A wins election based on addressing, with B coming in
2nd
then DR=A and BDR =B
If A fails, B becomes DR automatically
next, election is held for BDR, and C wins becase A is still down
when A rejoins, no elections, and it is stuck with neither job
From there, you might reset OSPF on router B to try to force DR election, but
again, C becomes the DR automatically (BDR moves up to DR without election)
Next, BDR election happens and Router A wins the title.
Now if you reset OSPF on router C, router A would finally end up as DR again.
(BDR move up to DR)
This behavior is one of the reasons why you might disable the use of a BDR on
a hub and spoke NBMA type of network by using priority statements (a wrong DR
here is worse than no DR!).
-
Doug
________________________________
From: nobody@groupstudy.com on behalf of Bill.McKenzie@bisys.com
Sent: Tue 3/14/2006 8:56 PM
To: Sam K.; ccielab
Subject: Re: Simple OSPF question
Nothing. There is no preemption,
So the first DR doesn't take back over
----- Original Message -----
From: nobody
Sent: 03/14/2006 09:50 PM
To: ccielab@groupstudy.com
Subject: Simple OSPF question
Hi Group,
When the DR goes down then BDR takes over but what happens when the DR comes
back up?
Thanks,
Sam
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