When CUCM receives SIP INVITE message this is how it's being handled
*** LHS stands for Left Hand Side of SIP URI while RHS stands for Right Hand Side of SIP URI
Important Note: The Enterprise Parameter 'URI Lookup Policy' is set to case sensitive by default. This means that when CUCM receives INVITE message, it will make sure that the called alpha-URI matches with uppercase/lowercase. If this parameter changes, CUCM won't care about uppercase/lowercase.
Assume that the cluster has two Directory URIs, email@example.com which is local & Carlo@gmail.com which is remote. By default when the caller dials Carlo@gmail.com, CUCM will forward the call to remote cluster ignoring local directory URI due to case sensitive (assuming the SIP route pattern exists for route-string).
It's important to configure the following:
- Cluster FQDN (CFQDN) Enterprise Parameter - This can be the FQDN of single node in the cluster or multiple nodes in the cluster separated by spaces. It can be a wildcard as well such as *.cisco.com
- Top Level Organization Domain (TLOD) Enterprise Parameter - Single domain such as cisco.com
- Enable "Use Fully Qualified Domain Name in SIP Requests" in the SIP Profile of all SIP trunks. When it will be used?
- When LHS is numeric, the RHS of To header is always overwritten by the trunk destination (fixed in version 10 by making To header matching Req-URI) - You need this setting
- If the call is routed based on numeric LHS, the RHS of Req-URI header will be overwritten by trunk destination - You need this setting. If the call is routed by matching RHS against SIP Route Pattern, RHS of Req-URI is preserved.