BGP into OSPF

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Apr 2nd, 2009
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I have a router that is running both BGP and OSPF.

BGP is learning the default route from its BGP neighbor.

I was going to redistribute the default route into OSPF with a route map and the “redistribute” command but I noticed that once I configured OSPF with the “default-information originate” command OSPF learned the correct default route and propagated it.

Does this mean I don't need to add the “redistribute BGP” command to my OPSF configuration?

Is this a good practice?


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Giuseppe Larosa Thu, 04/02/2009 - 05:36
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Hello Thom,

ospf default-information originate checks if there is a default route installed in the routing table if there is an OSPF LSA type 5 for 0.0.0.0/0 is generated and propagated in the ospf domain.


unless you use the always keyword should the BGP session fall down the OSPF LSA will be removed.


This can be a good solution if this is your single exit point to internet.


in more complex scenarios you can invoke a route-map as option of default-information originate so that you can check from what BGP neighbor the 0.0.0.0/0 is received for example


you don't need to redistribute bgp into ospf for this.


Hope to help

Giuseppe


royalblues Thu, 04/02/2009 - 05:37
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When you configure the default-information originate command under ospf, it will generate & advertise a default route as long as it sees a valid entry in its routing table .


In your case the default is being learnt from BGP so when u configure the command under opsf it starts advertisign the default. If your requirement is to just propogate the default, you need not do redistribution


Narayan

rakesh.hegde Mon, 05/18/2009 - 19:43
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You can not redistribute a default route into OSPF. You have to originate it using " default-information originate " command.


HTH,

Rakesh

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