some questions on isis

case i)

here is my topology,





r1 and r2 are in area 49.0001.

r3 is in area 50.0001.



r3 is having 6 loopbacks


r3 advertises all 6 networks in isis


now when i try to generate level 1 summary of 

summary address level-1" on r2 


it is nor getting advertised to r1.

what is the issue ?.


case ii)




both routers are in same area.(say for ex 49.0001)


i configured "is-type level-1" in global routing process on both routers .

i am still  seeing a l1 neighborship.


again i configured isis circuit-type level-2 on both the router interface

now i couldn't see any neighborship.


i tought interface commands have more priority than the global routing process.

and iexpected a intra area  level 2 adjacency to be formed between routers.

but it didnt happened.






  • Unlike other features where you can override a global setting at the interface level, this is NOT the case with is-type.


    If you set is-type level-1 it applies to ALL interfaces. You cannot override this at the interface with circuit-type.


    In your case it sounds like you need R2 to be a level-1-2 router so you can't use the global is-type level-1 command.

  • Thanks for the clarification bobby1..


    can some one tell me about the summarization issue ?

  • I figured out the answer,Actually there are 2 ways.

    i)redistribute level-2 routes in to level-1 and then summarize it.

    ii)create multiple instance on r2 with level-1 adjacencies between r2-r1 and r2-r3 and then summarize the routes from r2-r1.




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