Add SIP Gateway to Cisco CUCM

Adding a SIP Gateway to Cisco CUCM requires creating a SIP Trunk in CUCM and configuring Dial peer on the SIP Gateway.

Steps

Open a web page to login to CUCM administration using CUCM IP address.
Choose Device - Trunk from the menu
Choose SIP Trunk from Trunk Type drop-down list, SIP from Device Protocol drop-down list, and keep the default None from Trunk Service Type drop-down menu
Click Next to continue with SIP Trunk Parameters Configuration
Enter a unique SIP Trunk name into the Device Name field (any name, but it may not match the gateway hostname) and optionally give it a description
Choose a device pool from the Device Pool drop-down list.
Enter the IP address of the desired Gateway
Choose a profile from the SIP Trunk Security drop-down list
Choose a profile from the SIP Profile drop-down list and then click save

Enter these commands
- Voice Service VOIP
SIP
Bind Control Source-Interface ..int used for SIP Communication...
Bind Media Source-Interface ..int used for SIP Communication...
Session transport TCP(default is UDP)
SIP Gateway Configuration (Call Routing)
To incoming calls to CUCM you need to create a dial peer to tell the gateway which calls need to be routed where, As below:
dial-peer voice tag VOIP
destination-pattern .... (Called Numbers that should be routed to CUCM)
Session Protocol sipv2 (this command is a must since the default Protocol on VOIP dial peer is H323)
Session Target ipv4:...IP address of your primary CUCM...
codec G711ulaw
dtmf-relay h245-alphanumeric

If you have redundant CUCM you will need to add a second dial peer with Preference of 1. and don't forget that you need to associate this gateway to route pattern on CUCM if you would like your outgoing calls to be routed through this gateway.
If you have redundant connections to CUCM then you should use the loopback interface in the bind interface command