NM-8T1-IMA and Multiple Carriers

[bill.hambly]

Can the NM-8T1-IMA module be used to multiplex across multiple telcom carriers (Sprint, MCI, etc) on point-to-point T1 circuits? Thanks.

[zsiddiqu]

Yes as long as they are point to point clear channel T1s with no telco restrictions about what to configure then you can treat theT1s between the two ima interfaces as back to back links regardless of who is providing the T1s. Now from service point of view it sometimes is beneficial to have the T1s from the same service provider so as to have one point of contact if there was break in service but from configuration point of view it should be fine.

Just to reiterate the above is true if Telco is not doing the inverse multiplexing operation and just providing clear channel T1s.

[bill.hambly]

Sorry if this is a simple question, but I have asked 4-5 other people in the telcom industry that all gave me different answers. What exactly is a "clear-channel T1"?

Thanks.

[zsiddiqu]

Well theoretically a clear channel T1 means the ability to provide a 64kb/s DS-0 for the customer. What I meant in this particular context is that there is no restriction from telco as far as what to configure on the T1s and how many channels to use on the T1 then you can utilize those T1s from different vendors for bundling an ima group.

[bill.hambly]

I have one last question for you on this project. Our goal is to connect two sites together with 3.0 Mbps, using two identicle 3620's with NM-8T1-IMA's, and clear channel T1's. I have these setup on my test bench connected via 2 T-1 crossover cables, with successful connectivity between each (i.e., can ping each other). The basic configuration for each 3620 is as follows:

int atm0/0

no shutdown

ima-group 0

int atm0/1

no shutdown

ima-group 0

int atm0/ima0

no shutdown

ip address 10.1.1.x 255.255.255.0

pvc 0/33

inarp 5

protocol ip (IP of router on other end of IMA link) broadcast

Is there any other ATM-related modifications to my configuration that may be required when we connect these routers to actual T1 lines (clock sources, etc)?

Thanks very much for your assistance!

[vmulhollon]

You may wish to review:

http://www.cisco.com/warp/public/121/imalinkdown.html#ex

Specifically:

"If a link delay exceeds the specified maximum, the link is dropped."