ISIS Levels

Unanswered Question
Aug 21st, 2008


I have a setup..

R1---(isis level 1 only)---R2---level 2 only)---R3

I have done the minimum, most required config. NO default route..

Cisco website says "Packets destined for an address that is outside of the L1 area are routed to the closest L1/L2 router to be forwarded on to the destination area."

If thats true I shud see a default route on R1 towards R2 ?


Gaurav Prakash

I have this problem too.
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Harold Ritter Fri, 08/22/2008 - 04:40


You do not see the deafult on R1 probably due to the fact that R3 has the same area id as R2.

R2 will only set the attached bit in its LSP it advertised in L1 if it has an adjacency to a router with a different area id.

The attached bit is what will tell R1 to use R2 to any route outside the level-1.

If you want to keep the same area ID on R3 and still have connectivity between R1 and R3, you would need to run a L1 or L1-L2 adjacency between R2 and R3.



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