EIGRP Metrics

[michael.kilpatrick]

Can someone tell me how the delay of a summary route is computed on the router that is advertising the summary route. I suspect that this might have something to do with the number of longer-bit routes that are contained in each summary route... but I can't find anything in writing, like the formula. Check out the following: 2 summary routes being advertised on the same router on the same interface. Why is there 2 different delay values??

.

scp7603-a5t-2#sh ip eigrp top 163.230.112.0 255.255.240.0

IP-EIGRP topology entry for 163.230.112.0/20

State is Passive, Query origin flag is 1, 1 Successor(s), FD is 2816

Routing Descriptor Blocks:

0.0.0.0 (Null0), from 0.0.0.0, Send flag is 0x0

Composite metric is (2816/0), Route is Internal

Vector metric:

Minimum bandwidth is 1000000 Kbit

Total delay is 10 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 0

scp7603-a5t-2#sh ip eigrp top 163.230.104.0 255.255.252.0

IP-EIGRP topology entry for 163.230.104.0/22

State is Passive, Query origin flag is 1, 1 Successor(s), FD is 3072

Routing Descriptor Blocks:

0.0.0.0 (Null0), from 0.0.0.0, Send flag is 0x0

Composite metric is (3072/0), Route is Internal

Vector metric:

Minimum bandwidth is 1000000 Kbit

Total delay is 20 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 1

[edmonds_robert]

I'm not sure if this is what you're looking for, but try the following link:

http://www.cisco.com/warp/public/103/eigrp1.html#5

[steve.barlow]

Why is the hop count different? I think that may be the heart of the issue. Any offset-lists or anything?

Steve

[seilsz]

Michael,

EIGRP summary routes use the smallest metric of the more specific routes.

-Zach

[sun816]

EIGRP summary route use lowest metric route's delay value which it respond to.

[ruwhite]

EIGRP pulls the metric of the best component which falls within the summary, and takes the component (vector) metrics from that component. So, if you have:

10.1.1.0/24 cost 100

10.1.2.0/24 cost 200

being summarized to 10.1.0.0/22, the the summary will pull the vector metrics from the lower composite metric route, which is 10.1.1.0/24. I hope that makes sense.

Russ