Re: DR election

[Acee Lindem <[e-mail]>]

Hi Dror,

Zebaida, Dror (Dror) wrote:
> I understand that if there is already a DR/BDR then R4 will not become the DR.

As described succintly in Russ White's e-mail below.

> However, when an interface transitions out of the WAIT state, if it thinks it is
> alone on the network, it declares itself the DR.  If after that, it connects to the
> network, there are 2 routers declaring themselves DR. In our case R3 and R4.
> At this stage, is a new DR elected, or does R3 remain the DR.
>
> The scenario I am describing is R4 is conneced to the network after it transitioned
> out of the WAIT state (after 40 seconds)

This really should never happen on a broadcast or NBMA network unless you have
some type of connectivity or an NBMA configuration problem. I have seen it happen
on an NBMA network if the existing DR and BDR are using the RFC 2328 appendix C
suggested X.25 poll interval of 2 minutes and all the DR eligible neighbors are
not configured as eligible on all the DR eligible routers. When it happens a new
DR election will be triggered and R4 will become DR. I believe R2 will remain
as BDR.

Thanks,
Acee

>
> Thanks
>
>
>
> -----Original Message-----
> From: Russ White [mailto:[e-mail]]
> Sent: Tuesday, May 13, 2003 2:56 PM
> To: [e-mail]
> Subject: Re: DR election
>
>
> As long as there is already a dr on the link, R4 would not take over as the
> DR. Or it shouldn't. Think of it this way: The DR isn't elected first, the
> BDR is. Then the routers attached to the link "discover" there is no DR,
> and promote the BDR to DR, and elect a new BDR.
>
> :-)
>
> Russ
>
> On Tue, 13 May 2003, Dror wrote:
>
>
>>Hi,
>>
>>I have a question regarding a DR election algorithm.  If I have a netowrk
>>with 3 routers R1,-R3, each having the same priority and with router IDs
>>0.0.0.1, 0.0.0.2, 0.0.0.3 respectively.
>>
>>After a DR election process is done, R3 will be DR, R2 will be BDR and R1
>>will be DR-Other.  This is the result of the DR election process since R3
>>has the largest router ID.
>>
>>If I add a new router R4 with router ID 0.0.0.4, do I expect R4 to become
>>the DR, or does it just become another DR-other since there is already a DR
>>in the network.
>>
>>Does the result depend on whether R4 is connected to the network when it is
>>still in the WAIT state, or the result is the same nevertheless.
>>
>>Thanks
>>Dror
>>
>
>
> __________________________________
> [e-mail] CCIE <>< Grace Alone
>


--
Acee