Parallel P2P IS-Is link

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Jul 24th, 2008
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Can some body tell me if i have two parallel link between two routers and having IS-Is point to point configure ( /30 network for each link).Does it impact any way if one link fails interms of IS-Is adj and failover time ?



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Giuseppe Larosa Thu, 07/24/2008 - 03:26
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Hello Chintan,

IS-IS is a link state protocol so the router can understand that the same node is at the remote end of both point-to-point links.(the net address is the exactly the same)

The same LSP data structure is sent out both links.

Of course if one link fails an IS-IS adj will go down but your router can still route and forward on the other link.

Both links are used in load-balancing if you don't configure different IS-IS costs.

Convergence is very fast just the time to rebuild the IS-IS adj on the restored link.

Hope to help


chintan-shah Mon, 07/28/2008 - 02:26
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Hi Giuseppe,

I have one link between two router having /30 and another link between same two router having /30. In that case this two router will have have Adj established on each link i mean both link or only on link. "show clns neighbour" or show isis neighbour" shows me remote router id two times with diff Circuit ID ??

I have been told by some one that it established adj on both link so now i am confused.



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