On Jun 24, 2010, at 8:53 AM, Andy Koch wrote:

> On Wed, Jun 23, 2010 at 22:00, Richey <myli...@battleop.com> wrote:
>> I've been looking around and can't find a clear cut answer to this question.
>> Is it possible to loop up a far end T1 smart jack using a PA-MC-T3 in a
>> 7206?

yes, there is.

> I believe the remote T1 loopback features are only for CSU/DSU.  The

fortunately for Richey, this is incorrect.

> to drop it without access to the CSU/DSU that I looped and manually
> clearing it (or inserting a T-BIRD and sending the right loop-down
> code).
> 
> If anyone else has experience in getting this to work, I would be
> interested to hear.

I suppose this can become a NIU/smartjack specific question. As far as I am 
aware, Cisco will send the proper bits in the FDL towards the, sending first 
the loopback enable command (which are stuffed into the 4kbit/sec FDL portion 
of the ESF header -- the other 4kbit of course are ESF CRC bits), and then 
sending loopback disable when the command is removed. This has worked fine in 
practice over several lec and clec TDM networks.

The commands that work for pa-mc-t3 and ct3-ip (yes, vip+7500 rocking out in 
2010 = awesome) are:

(config-if)#loopback remote line fdl ?
  ansi      Per ANSI T1.403 Spec. (remote CSU)
  bellcore  Per TR-TSY-000312 Spec. (remote SmartJack)

I have found the cisco mft-t1 VWIC's will respond to CSU loopback commands, and 
nearly every single ADC, adtran, etc NIU has worked fine given bellcore FDL 
loopback commands.

Of course, I have also noticed anywhere from a 15 to 20 minute 'forced loopback 
timeout' -- so doing extended tests can be confounded by 'blips' where the 
smartjack will auto-disable its loopback state.

-Tk


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