[c-nsp] SNMP OID to see if a Tn interface is looped up?

[Justin Shore]

Does anyone happen to know if there's an SNMP OID that one can query to 
see if a standalone T1, T1 channelized inside of a T3 or OC3, or a 
high-capacity TDM interfaces like a T3 is looped up at the CSU?  I've 
had an occasion where a T1 was left looped up by the local-loop provider 
that I didn't discover until troubleshooting the downed circuit the next 
day.  I'd like that type of event to be a warning-level event in Nagios 
(that gets made critical after a handful of hours in that state).  All I 
have to work with right now is down-when-looped which makes the NMS 
report that there's a full blown problem when in fact the interface is 
merely looped up for testing.  This data is reachable via show commands 
but I haven't had any luck with SNMP OIDs at this point.  It would take 
a hefty script to pull out loopback data from the controllers I imagine.

My Google-fu is failing me on this one.  Anyone have any SNMP 
suggestions?  Perhaps I can generate a SNMP trap for such an event.  I'm 
sure I'm not the only one worried about this or who's already faced it. 
  I don't want to be the one who accidentally forgot to loop down a CSU 
when my testing was complete.  This isn't really limited to TDM circuits 
now that there is support for Ethernet loopbacks as well (though I'd 
like to think that it would be harder to forget about Ethernet loopbacks 
than remotely-requested TDM loopbacks).

Thanks
  Justin