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New Member

Influencing ATM routing in EIGRP

We have two offices in our metro area that are connected by a 2MB ATM PVC. Each of these offices also has a 5MB ATM PVC to the same backbone router in another city.

Currently, the traffic between the two local sites is being routed through the other city because the routers are seeing the 5MB PVC as the fastest path. However, there is a lot of traffic between the two sites. Is there a way, other than static routes, to influence the path so that traffic meant to go between the two local routers is passed over the 2MB link? We have had some problems with this PVC going down, so we don't want to use static routes.

We are running EIGRP.

New Member

Re: Influencing ATM routing in EIGRP

Hi, EIGRP use 5 metrics for calculating the best path, bandwidth, delay , load, reliability and MTU.

Tweek the delay parameter so that the traffic follows the path you want.


Re: Influencing ATM routing in EIGRP

And please don't ever use bandwidth for weaking the path selection algorithm--other things rely on bandwidth that you don't want to mess up.



New Member

Re: Influencing ATM routing in EIGRP

Right now, the delay statement for the 5MB circuits is 200. The delay statement for the 2 MB statement is 1500. Do you have any suggestions for where to start tweaking? Should the 2MB PVC delay be changed to less than the 5MB delay? Does the 5MB delay also need to be changed?

Re: Influencing ATM routing in EIGRP


Its always better to make a single change, than making 2 changes.

So change the Delay of 5 MB from 200 to something greater than 1500 that is make it 1544...(T1 bandwidth value) . Thisis just an example. YOu can use any value above 1500.

command is...

int atm 0

delay 1544

Re: Influencing ATM routing in EIGRP

I forgot to include one more recommendation.

When you change delay, change the delay at both interfaces of the link, for optimal routing. If you are changing the 5MB interface delay on Router B, change the delay at other end (on other city) also. Otherwise packets from B will go on 2 MB first, and will return through 5 MB link.

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