OSPF Stub routing

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Nov 2nd, 2008
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Hi,

I have a OSPF stub router with uplinks to two ABR's. The Stub router is configured to be totally stubby, therefore why do I also see other LSA's as well as the default route from each ABR. I thought I would only see the default routes.

Thanks in advance for any help.




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Amit Singh Mon, 11/03/2008 - 00:33
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Paul,


The routes that as listed under the routing table as the "O" which are intra-area routes not the inter-area routes.


The most important thing to look out is your topology diagram. It looks like you have the router 1 as both ASBR and ABR as you are redistributing the BGP routes at the ASBR.


Areas that have external routes redistributed into them cannot be configured as stub or totally stubby areas.


External routes (like the Link State advertisement (LSA) type 5) are not allowed in stub areas. Therefore, they cannot propagate from the stub area into the backbone area, resulting in loss of connectivity to the external networks.


regards,

-amit singh

paul-giles Mon, 11/03/2008 - 01:12
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Thanks Amit.


I know there had to be a simple answer and one that I had easily overlooked.

Giuseppe Larosa Mon, 11/03/2008 - 02:50
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Hello Paul,

verify the config of the second ABR


O IA 199.28.142.0 [110/2] via 199.28.165.157, 01:28:58, GigabitEthernet0/2


you are receiving only one O IA in addition to default route and comes from 199.28.165.157.


verify you have

area 0.0.0.1 stub no-summary

on both ABR


Hope to help

Giuseppe


paul-giles Mon, 11/03/2008 - 18:00
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Thanks for you response Giuseppe.


Both ABR's have the stub no-summary command.


The reason I believe for the odd behaviour that I am seeing is that one of my ABR's is in fact an ASBR, which is not allowed for a NSSA or Totally Stubby topology.


Thanks.



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