[c-nsp] IS-IS Multiarea on 12.2 SR

[Oliver Boehmer (oboehmer)]

Jared,

> >> I've been having quite a few adventures with IS-IS over the last
few
> > weeks
> >> and have finally hit a wall, so I'm hoping someone here can give me
a
> > hand.
> >> Basically, I need to build a network with IS-IS multiarea as
described
> > here:
> >
http://www.cisco.com/en/US/products/ps6599/products_data_sheet09186a0080
> > 0e97
> >> 80.html
> >
> > I reckon you need to build this for IP? ISIS multiarea is only
supported
> > for CLNS routing, as stated in the above link under "Restrictions".
> 
> I do need this for IP routing, not CLNS. If the feature is only
supported
> for ISO CLNS and not IP routing, why does it work on my lab of 2600s
running
> 12.3 latest, with the exact same config, also in an IP-only
environment?

Well, don't really know. It's not tested, but it might work in some
environment/releases.. never looked at it really..

> Really, my only need is to prevent my L1 routers from learning the
entire
> area's routes, but my network design requires me to directly connect
my L2
> router to an L1 (i.e. no room for a L2/L1 between them). I just need
the L1
> routers to get a default towards its directly attached L2, and the L2
> backbone to learn the L1's routes. This is essentially a TS-NSSA in
OSPF. If
> there's some other way I can get this behavior with IS-IS, I'm all
ears.

Hmm, if you stick all L1s into the same area (i.e. "standard" design),
you can't prevent them from seeing the L1 LSPs from the other L1s in the
area. However you could investigate filtering the routes from being
entered into the RIB, similar to "distribute-list in" command in OSPF,
which doesn't exist in IS-IS. But you could try

router isis
 distance 255 ip 
 distance 115 0.0.0.0 255.255.255.255 10
!
access-list 10 permit 0.0.0.0

to have only the default-route in the RIB. Not sure if this helps, not
sure which problem you are trying to solve :)

	oli