Layer 1 Voice T1 Troubleshooting
Posted by Peter Kurdziel on October 27, 2009
Layer 1 Voice T1 Troubleshooting
Common problems
Misconfiguration at one end
Switch type must match
Channels must match
Clock must be opposite
Isdn protocol-emulate must be opposite
Dial peers coordinated
Layer 1 – needs to match
· Framing – ESF or SF (aka D4)
· Line coding – B8ZS (use with ESF) or AMI (use with SF)
· Cable length – Can induce attenuation if needed for short cables
· Clocking – MUST be set correctly – one side provides to the other
· Channels in use – Depends on protocol and call-control agent
Troubleshooting Commands for ISDN PRI
Show controller t1 x/y·
Show voice port summary·
Show isdn status (shows Layer 1 and Layer 2status)·
Show dialplan number {digits}·
Debug isdn q921·
Debug isdn q931 (most useful to see signaling)·
Debug voice ccapi inout
T1 CAS (Channel Associated Signaling)
Layer 1 – needs to match
· Framing – ESF or SF (aka D4)
· Line coding – B8ZS (use with ESF) or AMI (use with SF)
· Cable length – Can induce attenuation if needed for short cables
· Clocking – MUST be set correctly – one side provides to the other
· Channels in use – Depends on protocol and call-control agent
Troubleshooting Commands for T1-CAS
Show controller t1 x/y
Show voice port summary
Show dialplan number {digits}
Debug vpm sig (to see cas signaling)
Debug voice dspapi (to see the digits at low level)
Debug voice ccapi inout
Ref: Cisco techtorial
