[Isis-wg] an ISIS question

[Mike Shand]

At 08:54 01/12/1999 -0500, He, James wrote:
>I am thinking about a scenario like this: three ISIS systems R1, R2, and R3.
>R1 is a L1/L2 system with area addresses 1 and 2. R2 is a L1-only system
>with
>an area address of 1. R3 is also a L1-only system with an area address of 2.
>All three systems are connected via a LAN. Obviously the systems will
>establish
>L1 adjacencies to each other.
>
>Q:  R1 will have L1 adjacencies to R2 and R3. However, R2 and R3 will not
>be adjacent to each other as the two systems do not a common area address.
>Will R1 have two L1 link state databases as we have two L1 areas bridged
>by R1?  Normally different L1 areas are connected via different L1/L2
>systems.

No. All the systems will reside in the area with area addresses 1 & 2. You 
are correct that the adjacency between R2 and R3 will not come up and in 
any sensible implementation it will complain about an area mismatch.

>So we are looking at a degenerated case.

Yes, this is not a recommended configuration. In general you should always 
configure all systems on the LAN to have the same set of area addresses. 
The only exception to this is in the dynamic case where you are trying to 
add/remove/change an area address.

         Mike




>Thanks.
>
>
>James
>
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