This object is ifIndex of the interface which is associated
to the media gateway IP address.
For ATM interface, the IP address should be associated to
an existing PVC:
cmgwIpConfigIfIndex represents port of the PVC
cmgwIpConfigVpi represents VPI of the PVC
cmgwIpConfigVci represents VCI of the PVC
And one PVC only can be associated with one IP address.
If this object is set to zero which means the IP address
is not associated to any interface.