IS-IS protocol L1/L2

[ssuet]

Hi Expert

As we all know L1/L2 send attached bit toward L1 n Level area for Interarea routing

Some time it can introduce sub optimal routing .Like if i want to reach destination X the path to X from L1/L2 is more than the my neighbour Level1 router

Isnt   lack feature in IS-IS  that we have to bear Suboptimal routing because only way we can go outside from our area through L1/L2 or is there any work around

Your help will be highly appreciated

Thanks

[Kashif-rana · Accepted solution]

Hi Dear

By default the ISIS L1 area is total stub (no inter-area and external routes). L1 ISIS routers rely on default route from L1//L2 router (ASBR). Each L1 ISIS router installs the default route from the nearest L1/L2 router (ASBR). So it could cause the suboptimal routing for the inter-area or external routes. Which is expected behaviour.

You can just do the route leaking for inter-area and external routes from the ASBR if you want to avoid this suboptimal routing.

HTH

[Kashif-rana]

Sorry it was typo ..... I meant ABR not ASBR