Troubleshooting errors in your configuration during the CCIE Voice Lab is of paramount importance- you should be able to fix most of the problems you encounter in a matter of minutes if you are to have a successful day. Here are some useful debug commands that will help you troubleshoot problems related to IOS gateways/ gatekeeper.
debug gatekeeper main 10: This command can be used on a gatekeeper and will show you how the gatekeeper will process an ARQ message received from an H323 gateway (including UCM). Cisco have published a decision tree that depicts the logic of how gatekeeper will handle an ARQ- this debug correlates to that decision tree.
debug gatekeeper call 10: This command can be used in tandem with “main 10″ and is primarily used to show the bandwidth requested in the ARQ message being sent from gateway to gatekeeper.
debug ras: Whereas the two commands above are useful to determine the logic of the steps used to get to ACF from ARQ, the debug ras command is used to see a high level view of all RAS messaging that is sent between GW and GK. The nice thing about this command is that it is not too expansive and shows ip addresses of source/destination devices in decimal.
debug h225 asn1: If all else fails then use this command. This will show the entire H225 and RAS message in ASN.1 format (they are very big messages!). This is useful to see information that is contained within a 225/RAS message such as the Calling/Called #, Source/Destination IP Address/Port #, Release Cause, etc, etc.
debug h245 asn1: This command will display the Terminal Capability Set, Master Slave Determination (MSD) and Open Logical Channel (OLC) messages once a call through an H323 gateway has been answered by the Called Party.
debug voip dialpeer: Very useful (perhaps the most useful within IOS gateways along with debug isdn q931) command that shows which inbound and outbound dial-peer has been matched after a call to the IOS gateway has been made.
debug voip ccapi inout: This debug command will show you what dial-peers are being matched on the IOS gateway and the state that the gateway is in during the processing of a particular call. It is also useful to see what codecs are being selected for each of the two call legs that represent the call.
debug voice translation: This command will display details of matching voice translation profiles that are invoked from within a dial-peer or voice-port during call processing.
debug sccp events: This command will let you know whether your media resources present on the IOS gateway are successfully registering to UCM/CME and also if they are being invoked during call processing.
debug ccsip messages: Very useful command to display SIP messages sent between the IOS gateway and SIP phones, SIP Providers and also Unity Express.
Vik Malhi – CCIE #13890
Managing Partner / Instructor – IPexpert, Inc.