I have a C2621 with an E3 ATM controller.
I loose connection with telco every two or three seconds, but telcom says that everything is fine, and have pretty much changed everything to troubleshoot.
I have been told that telco will give the clocking for the circuit, show diag, indicates that the source of the clock is from line, but I have configured for internal.
Clock Source INTERNAL (but the source of this clock is derived from LINE)
There is no controller level command to change it, and atm clock line does not work.
lim-ptl-c2621(config-if)#atm clock ?
INTERNAL Internally generated TX clock
lim-ptl-c2621(config-if)#atm clock LINE
% Invalid input detected at '^' marker.