[c-nsp] T3 fixed when cables are reseated..

[Jay Hennigan]

Richey wrote:
> I had this happen a year or two ago on another router on a different card.
> I have a 7206 with a PA-MC-T3 with about 25 T1s go down tonight.   I
> couldn't fix it remotely so I drove to the office to see what was going on.
> I unplugged the TX cable and plugged it in and then the same with the RX
> cable.   I went back checked the T3 and all of the T1s were backup.    Has
> anyone had this happen before?   I can't find any clues as to what happened.
> My only guess is that the far end is looped when I unplug the cables and it
> may reset the far end.  

If the T3 cable run is fairly short I've seen issues with Cisco PAs 
getting screwy because the signal level in to the PA is too high, 
regardless of the cable length setting (which just affects the 
transmitted level).  Usually this just manifests itself as a constant 
low-level stream of errors.

The fix is an attenuator inline with the receive jack on the port 
adapter.  10dB seems to do the trick.

http://www.pasternack.com/product-75-OHM-BNC-ATTENUATOR-DC-TO-1-GHz-1-WATT-PE7009-10-71538.html

Where size matters:

http://tinyurl.com/csb7rt

If the far end were looped, you would see the loop on "show interface" 
and unplug-replug wouldn't fix it.

Also verify clocking is provisioned correctly, that there is exactly one 
clock source on the T3.

--
Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
Impulse Internet Service  -  http://www.impulse.net/
Your local telephone and internet company - 805 884-6323 - WB6RDV