OSPF configuration on 6500

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Jan 13th, 2008
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i want to use OSPF to route between two Catalyst 6500 how can i control DR and BDR ( in routers i can create loopback interfaces but in swtches i don't know how) please advice

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ankbhasi Sun, 01/13/2008 - 07:19
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Hi Friend,

You can configure loopback interfaces on layer 3 switche also. If you cat6k is running IOS then it is very well capable of supporting loopback interfaces.



mohammedmahmoud Sun, 01/13/2008 - 07:20
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Same logic on routers and L3 switches no difference:

DR Election -> The router with the highest ospf priority (per interface value, 0-255, default 1 and can be changed using ip ospf priority under the interface, and 0 means never), and if tie, the router with the highest RouterID (manually set via router-id, or the highest loopback/physical interface).

As best practice if you want to make sure that a certain router (L3 switch) is always the DR, configure the priority of the router (L3 switch) that you don't want to be the DR to be 0, thus it will never get into the election and you will be dead sure that the other will be the DR with no chances for the first router to boot to be the DR (since OSPF DR election doesn't apply preemption).


Mohammed Mahmoud.


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