Core Issue
The outbound calls through the H.323 Cisco IOS gateway from Cisco CallManager work fine. But, inbound calls fail.
Cisco CallManager does not respond to the H.323 gateway setup request. The Transmission Control Protocol (TCP) handshake to the Cisco CallManager disconnects immediately. There is more than one IP interface on the voice gateway. A loopback IP address is configured as the H.323 gateway IP address on Cisco CallManager.
The inbound call fails in the Survivable Remote Site Telephony (SRST) mode as well.
Resolution
In order to resolve the issue, configure the h323-gateway voip bind srcaddr x.x.x.x command under the source interface, where x.x.x.x is the IP address of the interface itself. Note that x.x.x.x must be the same IP address that is configured in Cisco CallManager for the H.323 gateway.
If inbound calls still fail, remove the direct-inward-dial command from the plain old telephone service (POTS) dial peer in order to use two stage dialing. Then, Telco sends the Dialed Number Identification Service (DNIS) digits to the router after it senses the dial tone.
Also, in the SRST mode, if the Telco sends a different number of digits, the direct-inward-dial (DID) configuration causes issues. If the voice ports already have signal DID, the direct-inward-dial command is not needed.
