Re: Waiting State Question

Mukul Goyal <mukul@UWM.EDU> Thu, 19 May 2005 18:14 UTC

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Date: Thu, 19 May 2005 13:14:22 -0500
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From: Mukul Goyal <mukul@UWM.EDU>
Subject: Re: Waiting State Question
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My guess is that if an interface comes out of the waiting state on receiving a
Hello from DR (without having received a Hello from BDR), it may elect itself
as BDR. This way many routers may elect themselves as BDR. Now all these BDR
claimants (except one) will ultimately take their claims to BDRship back but in
the process each router on the LAN may have to do several DR elections.

Here is a paper we wrote recently that may shed further light on this:


Quoting John Smith <jsmith4112003@YAHOO.CO.UK>:

> Hi,
> When a router comes up it starts the Wait Timer before it elects the DR/BDR.
> It either
> waits for the Wait Timer to expire or it waits for a router declaring itself
> as the BDR
> before it decides that it needs to get out of the 'Waiting' state (it does
> this by
> generating the Backupseen event).
> My question is why does it wait only for the BDR? Why not the DR? It can when
> it recieves
> a HELLO from the DR know that their exists a DR and a BDR. Why not then get
> out of the
> 'Waiting' state?
> Thanks,
> John
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