about the model on 7500 PA-MC-STM-1SMI

[w.zhanghua]

cisco said "The port adapter enables users to channelize an STM-1 down to 64 kbps using a variety of encapsulations on as many as 256 logical channels."

we know the stm-1 ,the speed is 155M, 155m/64K=2421,

how come the 256 logical channels? it should be 2421 channels

[donewald]

I am sure this has to do with the IDB limitations of the box that you are using this PA in and an allocation issu within each of the 63 controllers "Up to 256 usable channels can be allocated among the 63 E1 ports" . You're using a 7500 here, that in recent IOS teh IDB limitation is 2048. So if this was not throttled down from NX64 not only would this PA be capable of taking all possible interface descriptors but taking more than the 7500 could handle. 256 seems like a number to make it play nice in the router as to not take more than it's share of IDB's rather than a HW limitation. Also I am sure that the Developers do not think that using this PA most customers would be provisioning many 64k circuits. Just a guess there.

Here is a link on IDB's.

http://www.cisco.com/warp/public/63/idb_limit.html

Hope this helps,

Don