EIGRP Max. Successors

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Nov 16th, 2007
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what can be the max no of successors in eigrp for reaching a particular destination when we check with " sh ip eigrp topology " command.

i have multiple routes to reach a destination in my network but when i check with the above mentioned command it shows me only 2 next hops to reach that destination one hop with the feasible distance and 2nd with the next higher distance that is of the successor,

can anybody guide.



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Kevin Dorrell Fri, 11/16/2007 - 03:10
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IT could be that the rest are failing the "feasible distance" check, which is the main loop prevention mechanism in EIGRP. That is a neighbor cannot be a feasible successor if its metric to the destination ("advertised distance") is greater than mine. That is, if he is further from the destination than I am, he cannot be a successor.


Note this is his distance to the destination, and not what mine would be if I routed through him.


I can take an alternate route, yes, but not if that alternate route is via some point which is further from my destination than I am already.


Kevin Dorrell

Luxembourg


Richard Burts Fri, 11/16/2007 - 04:23
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Perhaps we need some additional information from Susheel. To answer his specific question about what is the maximum number of successors I am not sure what the absolute maximum would be (if in fact there is one) but believe that it would be at least as large as the value of maximum paths which is 16 in some versions of code.


Lets also clarify whether we are talking about successor or successor plus feasible successor. I understand the original post to be about successor. Susheel can you post the output of show ip route which shows multiple paths to a destination and post the output of show ip eigrp topology which shows the number of successors? This would help us understand what is going on and perhaps to answer your question.


HTH


Rick

susheel.p Wed, 11/21/2007 - 03:14
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How does EIGRP calculate Feasible Distance.

when checked with " sh ip eigrp topology " the values in brackets in via line are in a/b format.

where a is the distance or the metric to reach the specified destination, what does b values specify.


Kevin Dorrell Wed, 11/21/2007 - 03:49
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b is the metric at the next hop .. the so called "advertised distance".


Kevin Dorrell

Luxembourg


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