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Community Member

Successor and Feasible Successor

Hello,

In EIGRP, if Successor route fails and there is no feasible successor route available, how EIGRP will react?

Thanks

1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

Re: Successor and Feasible Successor

There are sometimes the situation happens that you have described above. If that happens the EIGRP declares the route as SIA " Stuck in Active " routes. When you do " show eigrp active " its lists the router address from which the reply is pending and then you can troubleshoot the issue.There could be some problem with the router, may be some bandwidth issue, some link issue due to which a reply is pending.

Please see the link below for more information:

http://www.cisco.com/warp/public/103/18.html

HTH,

-amit singh

4 REPLIES
Community Member

Re: Successor and Feasible Successor

Hi,

The short answer is that (DUAL) recomputation occurs when no feasible successor route exists.

Details:

If a route becomes unreachable e.g. the link to the Successor fails, then the router looks in its Topology Table

for another route with a lower metric than its Feasible Distance i.e. a Feasible Successor, and that one becomes the Successor.

This requires no neighbour querying and is therefore very fast.

If no feasible successor exists,

- queries are sent out to the network

- Diffusing computation is performed to select another feasible route

HTH

Thanks

Community Member

Re: Successor and Feasible Successor

Hi,

Your answer assured me about what I was thinking. Thanks alot.

My only doubt is, the time waiting to send the queries and find a new successor route, what will happen to packets destined to failed route?

Thanks again.

Cisco Employee

Re: Successor and Feasible Successor

There are sometimes the situation happens that you have described above. If that happens the EIGRP declares the route as SIA " Stuck in Active " routes. When you do " show eigrp active " its lists the router address from which the reply is pending and then you can troubleshoot the issue.There could be some problem with the router, may be some bandwidth issue, some link issue due to which a reply is pending.

Please see the link below for more information:

http://www.cisco.com/warp/public/103/18.html

HTH,

-amit singh

Community Member

Re: Successor and Feasible Successor

Hi persepolis77,

If there is no route for the packets, they will be dropped, creating a black hole.

HTH, please rate all posts

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