DR/BDR Election

Answered Question
May 16th, 2007
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Hi all,


My understanding of the criteria for electing the DR/BDR is as follows:


1. OSPF priority on the interface. If they priority is the same, then,

2. The router with a loopback address configured, irrespective of the value. If both routers have the loopback configured, then

3. The router with highest RID on any interface.


OR THEN IS IT...


1. OSPF priority on the interface. If they priority is the same, then,

3. The highest RID (which is the highest IP on the ANY interface).


Which one is correct? Can somebody kindly point me to some references on this?


Kind regards.

Correct Answer by mohammedmahmoud about 9 years 10 months ago

Hi,


For example:


router ospf 1

router-id 10.10.10.2


If not set this way, the router will take the highest ip address as its RID.


HTH, please do rate all helpful replies,

Mohammed Mahmoud.


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mohammedmahmoud Wed, 05/16/2007 - 13:39
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Hi,


Highest priority then highest RID.


NOTE RID is unique thus it cant be the same on more than a router on the same network, but the idea is that if the RID is not manually defined it is taken as the highest loopback ip on the router.


HTH, please do rate all helpful replies,

Mohammed Mahmoud.

network_enginee... Wed, 05/16/2007 - 13:54
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Hello!


Thanks for the reply. So, how would I set the RID manually? Or did you mean that set the highest possible IP on the router manually, so that becomes the RID?`


Kind regards.

Correct Answer
mohammedmahmoud Wed, 05/16/2007 - 14:01
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  • Green, 3000 points or more

Hi,


For example:


router ospf 1

router-id 10.10.10.2


If not set this way, the router will take the highest ip address as its RID.


HTH, please do rate all helpful replies,

Mohammed Mahmoud.


srue Thu, 05/17/2007 - 07:34
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as a side note, if you manually change the priority on an interface or the RID, you have to clear the ospf process for the new values to take effect.

clear ip ospf process

or

clear ip ospf process_number process

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