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New Member

CLNP/ISIS Topology Advice

hi,

i have attached a basic diagram of a topology for a network that's running CLNP using ISIS routing services.

As yo ucan se we have 3 POPs, each one in a different ISIS area and a backbone area.

My question is very specific (if posible):

in the diagram you can see the relationships between routers. in between POPs the relationship is L1/L2. within the POP, adjacencies are forced to L1.

i would agree that intra-area routers should be L1 adjacent, but since (for example) r1 and r2 are both backbone routers, shouldn't they have an L1/l2 relationship?

please advice.

regards,

c.

1 ACCEPTED SOLUTION

Accepted Solutions
Purple

Re: CLNP/ISIS Topology Advice

Hi,

The relationship between r1 and r2 has to be L1/L2, provided that there is a direct link between them. One of the fundamental requirements of ISIS is that the level 2 backbone has to be contiguous. So you have to make sure that the link between r1 and r2 is L1/L2.

Hope that helps - pls do rate the post if it does.

Paresh

3 REPLIES
Purple

Re: CLNP/ISIS Topology Advice

Hi,

The relationship between r1 and r2 has to be L1/L2, provided that there is a direct link between them. One of the fundamental requirements of ISIS is that the level 2 backbone has to be contiguous. So you have to make sure that the link between r1 and r2 is L1/L2.

Hope that helps - pls do rate the post if it does.

Paresh

New Member

Re: CLNP/ISIS Topology Advice

thanks, paresh. i do not have that much experience with isis, but i thought so.

there is a direct LAN link between r1 and r2.

thanks, again.

Purple

Re: CLNP/ISIS Topology Advice

No probs mate...

I should mention one other thing... You can maintain a contiguous L2 network in other ways too. For example, if you had another router, r3, between r1 and r2 (in addition to the direct link between them), you could run in L1 mode over the direct link provided that both the r1-r3 and r3-r2 were running L2...

Hope that helps.

Paresh

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