[c-nsp] DS3 mux issues - SOLVED

Justin Shore justin at justinshore.com
Wed Dec 10 12:16:04 EST 2008

Justin Shore wrote:
> We're staging a DS3 mux to aggregate T1s back to a PA-MC-2T3-EC in a 
> 7206VXR (G2) running 12.4(15)T7.  I haven't channelized a T3 before so 
> I'm feeling my way through this.  It looks to be relatively simple but 
> I'm getting tripped up somewhere.  On the 7206:

We just solved the problem.  After soldering the tech's TBird back 
together he hooked it up and quickly figured out that the T & R pairs 
were flipped.  He took care of that and the T1s popped up right away.  I 
believe it was Jonathan Herbert who first suggested that as a possible 
culprit so many thanks to him.  That would explain why the circuit would 
come up with physically looped because it wouldn't matter if T & R were 
flipped at that point.  But of course when the routers themselves would 
never make the connection on their own.

So at this point I'm generating clocking on the DS3 from the 7206; the 
7206's DS1 are set to get clocking internally; the mux is set to get 
clocking off the DS3 from the 7206; and finally the CPEs are always set 
to line for clocking.  I'm currently running with M23 on the DS3.  It 
was suggested that I switch to cbit for better diagnostics in the event 
of DS3 failure.  I'll test that this afternoon.

Many thanks for all the help.  In the end we were tripped up by a simple 
L1 problem.  Thanks again


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