From: Todd, Douglas M. (DTODD@PARTNERS.ORG)
Date: Tue Nov 06 2007 - 06:24:55 ART
General information via cisco:
This should do the trick:
The DR is elected either by the priority or when the priority is the same by the
highest RID. So - either you can use router-id x.x.x.x and make sure it's the
highest of the two or use the priority command.
Info:
http://www.cisco.com/warp/public/104/2.html
DR Election
DR and BDR election is done via the Hello protocol. Hello packets are exchanged
via IP multicast packets (Appendix B) on each segment. The router with the
highest OSPF priority on a segment will become the DR for that segment. The same
process is repeated for the BDR. In case of a tie, the router with the highest
RID will win. The default for the interface OSPF priority is one. Remember that
the DR and BDR concepts are per multiaccess segment. Setting the ospf priority
on an interface is done using the ip ospf priority <value> interface command.
A priority value of zero indicates an interface which is not to be elected as DR
or BDR. The state of the interface with priority zero will be DROTHER. The
following diagram illustrates the DR election:
-----Original Message-----
From: nobody@groupstudy.com on behalf of Tarun Pahuja
Sent: Mon 11/5/2007 4:51 PM
To: M_A_Jones@dell.com
Cc: ephillips@squick.cc; ccielab@groupstudy.com
Subject: Re: Any way to force OSPF DR other than "priority 0"?
Please read Page 274 in the following link:
http://books.google.com/books?id=dKzpj4r7KCwC&pg=PA271&lpg=PA271&dq=how+to+make+
sure+hub+becomes+dr+nbma&source=web&ots=qLxRT9QU7K&sig=xF6TIxQYrQDUEDAwKic9JjVa1
3Q#PPA274,M1
HTH,
Tarun
On 11/5/07, M_A_Jones@dell.com <M_A_Jones@dell.com> wrote:
>
> Im thinking in theory, that is what they'd be looking for (Setting
> others to 0 and setting a high priority for DR). Most people arent aware
> how important the speed of the routers boot up phase is during election.
>
>
> So I doubt you'd see something like that. I to, did a lot of digging for
> that very instance.
>
>
> Michael Jones
> Network Engineer
> Global Network Operations
> Dell Inc.
> 512.723.3268
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Eric Phillips
> Sent: Monday, November 05, 2007 11:05 AM
> To: ccielab@groupstudy.com
> Subject: Any way to force OSPF DR other than "priority 0"?
>
> Hey all,
>
> I have done quite a bit of Googling and DOC-CD reading, and have not
> found anyone offering any clever ways to force the election of a certain
> router as the DR besides setting the priority to 0 on all other routers.
>
> For example, if I had a question that asked me to ensure Router1 was
> always the DR on a certain segment without touching the configuration of
> Router2 and Router3 I can set the priority very high on Router1, but if
> Router1 boots a few seconds later than Router2, Router2 will be the DR
> even if it has it's default priority of 1. The only way I can think to
> completely guarantee Router1 is always the DR is to make the priority 0
> on all other routers.
>
> Am I missing something obvious, or am I over thinking this too much? I
> have not seen this asked in any practice labs, just theorizing what
> could happen.
>
> -Eric
>
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