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Webcast-Catalyst9k
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OSPF ASRB/ABR

Can an ASBR have an area configured as stub? I know it is not a good idea to have an ASBR configured as a TSA due to non-standards, external routes and redistribution issues. What are potential issues that could arise using stub?

Thanks

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New Member

Re: OSPF ASRB/ABR

If you're considering placing an ASBR inside a stub area, then it's a no-go.

Remember that external routes in a stub area are replaced by a single default route, and that you cannot have other external routes in a stub area.

The area would have to be NSSA (Not-So-Stubby-Area) for the ASBR to inject external routes into your network inside the NSSA.

The external routes show up in the NSSA as type 7 LSAs and are converted to type 5 LSAs at the ABR. You can filter/summarize type 7 LSAs at the ABR.

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