Friday, 28 October 2011

MGCP Control of a Fractional PRI

Using MGCP usually makes life much easier with Communications Manager, but unfortunately it does assume that any PRI circuit is using the full amount of channels (23 for a T1 or 30 for an E1) and therefore doesn't support fractional PRIs.
Here's how to kludge MGCP into using a fractional PRI in 7 easy steps, for this example I'm using an E1 in slot 0/0/0:

1) Configure the gateway as normal in Communications Manager, then on the gateway use the ccm-manager config commands to configure it automatically:
ccm-manager config server x.x.x.x
ccm-manager config

2) Shutdown the voice-port:
voice-port 0/0/0:15
 shutdown
controller E1 0/0/0
 shutdown

3) Remove the ISDN layer 3 binding:
interface Serial 0/0/0:15
 no isdn bind-l3 ccm-manager

4) Replace the pri-group:
controller E1 0/0/0
 no pri-group
 pri-group timeslots 1-x service mgcp

5) Restore the ISDN layer 3 binding:
interface Serial 0/0/0:15
 isdn bind-l3 ccm-manager

6) Enable the voice-port:
controller E1 0/0/0
 no shutdown
voice-port 0/0/0:15
 no shutdown

7) Disable auto-configuration downloading, otherwise Communications Manager may undo your hard work:
no ccm-manager config
copy running-config startup-config

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