Maheshwar, You can also check the SIP Trunk configuration checklist from this page
http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/admin/7_0_1/ccmsys/a08sip.html#wp1126527
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Each SIP trunk must have a unique SIP routing configuration for SIP routing to work. Cisco Unified Communications Manager uses a combination of information from incoming SIP messages to route the SIP message to the correct SIP trunk. Be aware that a SIP trunk routing configuration is unique if the following statements apply:
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No other trunk gets configured with the same values for the Incoming Transport Protocol, Incoming Port, and Destination Address fields.
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No other trunk gets configured with Transport Layer Security (TLS) selected as the Incoming Transport Protocol and the same values in the Incoming Port and X.509 Subject Name fields. The X.509 Subject Name parameter can comprise a list of names.
It has also listed out some SIP trunk examples.
//Suresh
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