What is SIA in EIGRP

Unanswered Question
Apr 6th, 2009


What is the expansion for SIA. And explain in possible.

I have this problem too.
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lamav Mon, 04/06/2009 - 10:27


I can understand why Jon offered that link. The explanation can be a long one and would probably require more explaining than its worth, since its already there for you to read.

In short, though, in eigrp, when a route to a destination network is "passive" it means that the routing process is satisfied that it has a valid successor (primary route) to the destination network.

If it loses that route, and it does not have a feasible successor in its eigrp topology table that it can use as a new primary route, the eigrp routing process will mark the route as "active" and run the Diffuse Update Algorithim (DUAL). It will query all its neighbors regarding an alternate route to the destination.

That neighbor router will in turn query all its neighbors, and so on and so forth. All the queries must be replied to. If one router does not reply, the route will be Stuck in Active.

This is a very basic explanation, just to supplement that technical egghead talk you're going to encounter in the document. :-)



CriscoSystems Mon, 04/06/2009 - 13:26

This is a thing I've always had trouble understanding about EIGRP. If the neighbor routers; the ones being queried; had another route to the destination, wouldn't they have already reported it to all of their neighbors, including the querier? What with EIGRP being a link-state protocol, where all routers build a complete topology table and all...

Mohamed Sobair Mon, 04/06/2009 - 11:40


Adding to Jon's and Victor's:

The route in the Eigrp marked with SIA when the neighbor doesnt answer to the original query, the reason behind this could be one of the following:

1- High delay on alink.

2- Hardware failure.

3- insufficient Memory resource to handle query reply packets.

Additional note: when the route remains In "SIA" state, the neighbor relationship is reset between the original Querier and its neighbor.




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