Re: OSPF understanding

Hi Nadeem,
This is a frame relay thing....

The other routers cannot connect to R4 on layer2 so they use the only
available mapping they've got which is R5

They can only get to R4 when ospf is already running and they need a DR to
do so which has to be R5. But R5 has a mapping to R4 so it can use that as
its own DR. Hope you understand this.

In real life, this is bad network design though. When running hub and spoke,
you only want your hub to be DR.

HTH

Bobola Oke

On Thu, Feb 11, 2010 at 7:49 PM, Nadeem Rafi <nrafia_at_gmail.com> wrote:

> Hi GS,
>
> working with OSPF HUB and spoke, R5 being hub, R1 - R4 being spokes (using
> non-broadcast network type, all routers using physical interfaces). Spokes
> dont have direct frame-relay mappings with each other, but through hub.
> Made
> some experimental changes in this way.
>
> 1- make R5 DR by using priority
> 2- R1-R3 set ip ospf priority 0
> 3- R4 set priority lower than R5 but non 0.
>
> R5 becomes DR and R4 BDR, every thing works fine, other three spokes get R5
> as DR.
>
> Now cleared the R5 OSPF Process and R4 Become DR and R5 elected as BDR.
> Vriefied both on R4 and R5 by show ip ospf int command.
>
> BUT , other three spokes, R1-3 are still identifying R5 ad DR. Why? As for
> as i know, DR/BDR is proprty of interface not router. When R5 is BDR with
> R4
> on same interface then how come it can be DR for other routers on same
> interface?
> Interestingly, Database identifies correct DR, but show ip ospf neighour
> command don't reflect it correctly.
>
> Any input will be of great value.
>
> Best Regards,
>
> Nadeem Rafi
>
>
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Received on Thu Feb 11 2010 - 20:51:48 ART