Is there any possibility that losing network connectivity to call manager will bring down ISDN D channel on voice gateway or it is totally non related? I am running MGCP between voice gateway and CCM.
Absolutely. With MGCP, the ISDN Q.931 is backhauled to the CUCM. This means that CUCM controls the D+B channels. If CUCM is dropped (fault in host, network, etc.) then your Q.931 protocol exchange ceases and your D-channel (and B-channels) are dropped.
Please remember to rate helpful posts.