There are a variety of commands available for the purpose of monitoring ISDN connectivity, as outlined below.
- show isdn active. This command displays information about the current ISDN call, including the number dialed and whether a call is in progress.
- show isdn status. Displays the status of all ISDN interfaces, providing information relating to OSI layers 1 through 3.
- debug isdn q921. Displays link access information about ISDN D channels at the Data Layer. To make this command easier to remember, just relate the “2” in the q921 keyword as the associated OSI layer.
- debug isdn q931. Displays information about ISDN call setup and teardown on ISDN D channels at the Network layer. To make this command easier to remember, just relate the “3” in the q931 keyword as the associated OSI layer.
- debug dialer. Displays information relating to call setup and teardown.