The list trace command when used with the tac argument can trace calls using different trunk groups in your system. In order to run the list trace tac command you will first need to pick which trunk group you call is coming in or going out on and figure out its tac or trunk access code. This number will differ from system to system. Below we can see the second column of output contains our trunk access codes.
We run the list trace command from the CM SAT interface as follows list trace tac 892 where 892 is one of your trunk access codes obtained from the list trunk command in CM
We can use the Message Tracer form in CM to help filter our list trace tac output to only specific calls. This can be useful if you have a trunk that is extremely busy and you only need to zero in on one particular call. In order to do this we first need to figure out what type of trunk group we have.
When we want to filter our calls we need to make sure the trunk group is H.323, ISDN or SIP. Filtering using the MST form on an analog trunk is not possible.
Here in our example trunk group 2 is an ISDN PRI trunk. We can tell that because the Group Type: is isdn and the Carrier Medium: is PRI/BRI. Now that we have our group type we want to go to the change mst form.
On our change MST form we want to use page 2 if our trunk is an H.323 or PRI trunk. If we are using a SIP trunk we need to make sure on page 1 that SIP trunks are enabled which will open up a new page for us on the MST form.
Here we are essentially saying we will look for calls coming from 5551231234 into the system. The MST does not have to be enabled or running for this to work. With this value filled in we can then run list trace tac 892 /d and place a call into our system into trunk group 2. Since we have added the outside number we are calling from to the MST only calls from our number will show up in the output of the list trace command.
On "newer" systems (5.2.1 and later) we have the option to use the /c option with our list trace tac. This allows us to look at the calling party number in our list trace. For example list trace tac x5551231234/c would allow us to watch all of our trunks and only output data to our terminal when we place a call FROM 5551231234. The x allows us to filter. This can be useful where we don't know the exact amount of digits that me be presented to the phone system.
Example of list trace tac using /c filter