From: Peter Van Oene (pvo@xxxxxxxxxxxx)
Date: Thu Apr 05 2001 - 13:33:29 GMT-3
Hi Cory,
In ISIS, L1 routers form adjacencies with L1 and L1/L2 routers and L2 routers f
or adjacencies with L2 and L1/L2 routers. L1 routers will only form an adjacen
cy with other routers that have at least one matching area ID and L2 routers ar
en't concerned with matching area ID's. The backbone is simply the collection
of L2 routers.
That said, you could make your R2/R3 routers L1/L2 for this to work or you coul
d get fancy and make things all L1 and use multiple areas on R3 or R2. Or you
could make them all L2 or all L1/L2. Lots of choices :)
I highly recommend Jeff Doyles book for coverage on ISIS or, electronically....
[/being shameless plug]
i recently wrote a single area ISIS routing paper for www.certificationzone.com
which is currently available and might provide some insights. The paper is pa
rt of the Scaleable Link State series that Howard Berkowitz is managing and wil
l be followed up with a neat tutorial on ISIS routing in hierarchical networks
in the next few months.
[/end shameless plug]
Pete
*********** REPLY SEPARATOR ***********
On 4/5/2001 at 10:38 AM Hebert, Cory J (cory.hebert@wcom.com) wrote:
>Hi all-
>
>Here's the basic scenario: 4 routers running ISIS...
>
>r1-r2-r3-r4
>
>Easy enough. Well, r1 and r2 are in one area, and r3 and r4 are in a
>second
>area. My questions are: what should the router types of each router be?
>And also, do you have to define a backbone area? Lastly, if you do have to
>define a backbone area, do all of the routers have to be type L2 ?
>
>Please help! :)
>
>Cory
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