OSPF Strange problem

Answered Question
May 20th, 2007

I had 3 routers connected with one layer 2 switch in same vlan. Each router is configured with the loopback addresses like 1.1.1.1, 2.2.2.2 and 3.3.3.3. so as per the DR and BDR selectiong 3.3.3.3 should be the DR and 2.2.2.2 should be the BDR. but when i issue the show ip ospf neighbor command then its indicating the 1.1.1.1 as DR and 2.2.2.2 as BDR and all the router had same priority field.

I have this problem too.
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Correct Answer by ankbhasi about 9 years 6 months ago

Hi Friend,

Once the election is done and DR and BDR already elected the only option available to other routers to become DR/BDR is when existing DR/BDR go down.

So in your situation afaik the only option is to reload the router with having adress 1.1.1.1 and 2.2.2.2 and then 3.3.3.3 router will take the role of DR.

NOTE: If this is live network do not follow my suggestion of reload without arranging downtime or as per your company network requirements.

HTH

Ankur

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ankbhasi Sun, 05/20/2007 - 09:09

Hi Friend,

I believe your router having loopback ip 1.1.1.1 might be the first one to come online and router having 2.2.2.2 must be the second one to be online and is the reason 1.1.1.1 is DR and 2.2.2.2 is BDR.

Because there is no re-election for DR/BDR one which is already selected will stay as DR no matter there is other router having higher router ID or priority.

Can you confirm the uptime of all routers with "sh version" command?

HTH

Ankur

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dangal.43 Sun, 05/20/2007 - 09:18

yes you are correct so what will be the solution for that? how can i make the 3.3.3.3 as DR? so as per your reply if i will configure the ospf on router then the router which will be the first to enable the ospf it will become dr and then second enable router will be bdr. right!!!

so how can i correct this? even after the clear ip ospf process its continue with the 1.1.1.1 as DR and 2.2.2.2 as BDR.

Correct Answer
ankbhasi Sun, 05/20/2007 - 09:22

Hi Friend,

Once the election is done and DR and BDR already elected the only option available to other routers to become DR/BDR is when existing DR/BDR go down.

So in your situation afaik the only option is to reload the router with having adress 1.1.1.1 and 2.2.2.2 and then 3.3.3.3 router will take the role of DR.

NOTE: If this is live network do not follow my suggestion of reload without arranging downtime or as per your company network requirements.

HTH

Ankur

*Pls rate all helpfull post

dangal.43 Sun, 05/20/2007 - 09:25

thanks ankur this is not my production network. i am just doing testing on it. so as per your reply when i will save my config and will reload the routers then it will work as per the rule of OSPF DR and BDR election process. is that right?

ankbhasi Sun, 05/20/2007 - 09:30

Hi Friend,

Yes provided all routers are reloaded at a same time and come up same time. Also if you configure router 1.1.1.1 and 2.2.2.2 with priority 0 they will not participate in DR/BDR election and 3.3.3.3 will be selected as DR.

HTH

Ankur

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