Re: Waiting State Question

Kishore Rao <kishore@IND.ALCATEL.COM> Thu, 19 May 2005 19:11 UTC

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Date: Thu, 19 May 2005 13:08:32 -0600
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From: Kishore Rao <kishore@IND.ALCATEL.COM>
Subject: Re: Waiting State Question
To: OSPF@PEACH.EASE.LSOFT.COM
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Not NeighborChange but Backupseen

"If the neighbor is both declaring itself to be Designated
            Router (Hello Packet's Designated Router field = Neighbor IP
            address) and the Backup Designated Router field in the
            packet is equal to 0.0.0.0 and the receiving interface is in
            state Waiting, the receiving interface's state machine is
            scheduled with the event BackupSeen."

> I think the NeighborChange events are ignored while an interface is in
waiting
> state.
>
> Thanks,
> Mukul
>
>
> Quoting Kishore Rao <kishore@IND.ALCATEL.COM>:
>
> > The question was not about how DR or BDRs are elected. John's question
was
> > if the router should exit Wait Timer (and run DR election) on receving
Hello
> > from a router declaring itself as DR. Well, from section 10.5 it should.
> >
> > Kishore
> >
> >
> > > 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:
> > > http://cs.uwm.edu/~mukul/ospflan.pdf
> > >
> > > Thanks,
> > > Mukul
> > >
> > > 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
> > > >
> > > > Send instant messages to your online friends
> > http://uk.messenger.yahoo.com
> > > >
> >