Another Saturday, another day at work having fun with the fleet of Cisco devices that I manage.

Todays candidate: Cisco 3845 ISR Router - I must admit this is a pretty decent piece of kit, a single box solution that does all the normal networking and WAN connectivity but also can operate as a simple PBX and a voice gateway. Pop a ISDN card in, slap on a voice config and your laughing (or not!).

Tip of the day…If your ISDN PRI just doesn’t want to come up (and the endpoint won’t register in call manager) check the following.

1) Do:

debug isdn q921

If your circuit is in good shape you should see lots of debug mentioning that it wants to come up. You can also check by doing

sh isdn status

You’ll see that it’s sat in “TEI_ASSIGNED” mode.

2) shut/no shut your PRI. This will force it to go down and back up, this can sometimes bring it back in to life.

3) If all else fails then:

no mgcp

mgcp

This will force the gateway to pull down a config from the call manager and usually this will make the PRI register.

4) To check it’s registered do:

sh isdn status

You should see it in “MULTILINK_FRAME_ESTABLISHED” mode, this is expected behavior. To check calls are passing correctly do a: debug isdn q931. If you make some test calls you’ll see the traffic coming in and out. Remember to see this output you’ll need to do a term mon and remember once you’ve finished to do a no debug all!

Lunch time I think… and who stole my hour of sleep this morning!