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New Member

IMA - 3 T1s in an IMA group

We have three point-to-point T1s between two locations. They are connected to a 4 port IMA card which sits on a 3660 on each side.

The problem is that all 3 T1s show up in the group, but the traffic never goes over 2.667Mbps. Is there an issue. Here is the configuration of one side:

interface ATM5/IMA0

no ip address

load-interval 30

no atm ilmi-keepalive


interface ATM5/IMA0.1 point-to-point

description IMA to 237 Park

ip address

pvc 1/1

vc-hold-queue 400

New Member

Re: IMA - 3 T1s in an IMA group

A couple of questions...

What are you using to measure the bandwidth utilization?

When you look at the utilization, is it flat at 2.667Mbps or just peaks there occasionally?

Are you experiencing latency issues, drop packets, retransmissions?

New Member

Re: IMA - 3 T1s in an IMA group

Eventually found the problem thanks. There is a bug in the code. You have to remove the ATM IMA configuration from the router and re-apply it. You have to do this every time you add a new T1 to the group. It sucks, but you have to play the game I suppose. Thank full I dont have to reboot the routers.

New Member

Re: IMA - 3 T1s in an IMA group

You can check couple of things:

1) Any of your T1 flaps? "sh log", "sh int atmx/y"

2) "sh ima interface"- does all 3 t1s up and operational?

3)Do you have any drops on the IMA interface "sh int atm5/ima0"

4) Are you sure you are sending traffic more than 2.6M.

Here is the link for troubleshooting IMA:

For can open a tac case (800-553-2447) for more prompt troubleshooting,



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