Useful Debugs

There's a multitude of debugs on Cisco routers, below are some that I frequently find useful for VoIP troubleshooting:

Command	Purpose
debug ccsip messages	Shows the SIP messages being sent & received
debug gatekeeper call 5	Shows gatekeeper call processing, including bandwidth requests
debug gatekeeper main 5	Shows gatekeeper address resolution, including zone/prefix matching
debug h225 asn1	Shows H225 messages being sent & received
debug isdn q931	Shows ISDN Q931 messages, including calling & called number
debug ras	Shows summary of H225 RAS messages being sent & received
debug voice ccapi individual 2	Shows a summary of call setup messages regardless of protocol, including calling & called number
debug voip ipipgw	Shows the CUBE processing, such as when it needs to invoke a transcoder

Don’t forget to add voice iec syslog to your configuration too, this enables a lot of useful information to be logged.