Re: OSPF understanding

Thanks for input...

I know, this is bad design and the reason is also obvious as you stated. But
i am interested in how this is happening in back end. As i stated before,
DR/BDR is property of a interface, an interface can be only DR/BDR for an
interface/segment. Then how it come can be DR/BDR at the same time?
Please can you shed some light on how 224.0.0.6 address is
announced/selected?

On Thu, Feb 11, 2010 at 11:51 PM, Bobola Oke <okebobola_at_gmail.com> wrote:

> 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 Fri Feb 12 2010 - 00:14:26 ART