E&M Voice Trunk - Intermittant Modem Sync Losses

modem_guy · ‎10-20-2008

I am having issues with my modems running intermittant Sync loss and bit errors (5-20 minutes depending on speed). If I hook the modems up on a traditional TDM E&M line I do not see these errors. I have set up a lab environment with my 2 ISR's directly connected to prove that packet loss id not an issue. I have tried codec g711ulaw, and Clear Channel; both with the same results. I am seeing the same issue no matter what type of router I use - 3845, 2811, 2651XM ( all running spservicesk9-mz.124-17) I have attached the relavent configs.

Any suggestions would be greatly appreciated

vmoopeung · ‎10-24-2008

The problem is likely to occur when the pots leg is disconnected before the voip leg. If this occurs the port can go into this "stuck" state. Any subsequent calls will not ring the fax machine on this port. Temporary workaround is to "shut/no shut" the voice-port. This problem seems to be related to cisco fax-relay being invoked and it's interoperability with SCCP in this IOS version. Configuring:

voice service voip

fax protocol none

will prevent the problem from happening. Removing the SCCP config from the ports will prevent it from happening too