1. Navigate to System > Security > SIP Trunk Security Profile and select the Standard Non-Secured SIP Trunk Profile. Copy it and change Outgoing Transport Type to UDP. Save this as SIP Trunk Security Profile for ICE Telephony, and exit

2. Navigate to Device > Device Settings > SIP Profiles and select the Standard SIP Profile. Copy it and scroll down to Trunk Specific Configuration and set the Early Offer support for voice and video calls Required Field to Best Effort no MTP needed (default is disabled). Change the SIP options flag to ON (it is OFF by default). Save this profile as 'SIP Trunk Profile to test ICE Telephony'

3. Within the SIP Profile page, ensure that Session Refresh Method is set to Update. (It is Invite by default).

4. Create a SIP Trunk pointing to ICE Telephony Server with port 5060 and ensure you select your newly created custom profiles in the trunk. Set Call Classification as OnNet, and save this SIP Trunk.

5. Create the Route Pattern: Navigate to Call Routing > Route/Hunt > Route Pattern. Create a route pattern with dial number pattern used in your organization. These numbers will be used for users and channels in ICE Server. For example, 2001 to 2999 Directory numbers configured need to be routed via SIP Trunk, configure the route pattern as 2XXX as shown below and save. You need to configure channel DNs and user DNs in this 2001 to 2999 range. Make sure this range and Route Pattern is unique and does not collide with DNs configured on IP Phones registered to the same Call Manager to avoid conflict.

6. Now Call Manager SIP Trunk is ready to route the calls to ICE Telephony Server which will route it to DNs configured on ICE Server. Proceed to the next step (ICE Server Configuration).