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NM-1A-T3/E3 Sensitivity Issue


We need some urgent assistance here if anyone can help.

We have a new 34Mb ATM circuit between 2 sites. We have a 3825 router at one site and a 3640 at the other. Both routers have the NM-1A-T3/E3 ATM module installed. This module has a 75Ohm BNC Coax presentation which matches the circuit NTE.

The problem we are getting is that both ends of the circuit continually reset - the 3825 end stays up a bit longer (3-5 mins) but the 3640 end just constantly goes up/down.

We have checked the Carrier config and all seems ok, we have also changed the Coax cables at both sites to no avail.

Looking at the CCO documentaiton (and opening a TAC case) it seems the problem we are having is a known 'sensitivity' issue with these cards and Cisco advise to use the Coax Attenuator kit (ATTEN-KIT-PA=). Unfortunately, these are not readily available and our supplier is quoting 3-4 weeks lead time on gettting these. TAC don't seem to want to escalate this until we've tried the attenuators.

Looking on the web I have found some simular 75ohm Coax Attenuators which appear to be the same:

Would appreciate it if anybody could shed some light on this problem and if the above Attenuators are the same as the Cisco kit and will work - I can get these in 1-2 days.

FYI - the errors we're getting on the ATM controllers on each router are consistent with the Cisco known fault (Line Code Violation Errors etc) - these are visible when doing a 'show controllers atm2/0'

We have also tried a longer 50m Coax cable but without success.

Has anybody encountered this problem and had to use Coax Attenuators.?

We have other 34mb ATM circuits using the same kit without any problem.



Re: NM-1A-T3/E3 Sensitivity Issue

What is the ohmic value of the Coax Attenuator kit suggested ?If that is also 75 ohm, then i think you should not have a problem. It will work fine.

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