To properly configure an external SIP trunk on the UCx Server, perform the following steps.
External SIP trunks that are accessed via a router with NAT enabled, must have the following configured on the SIP Settings page:
Enable RTP port forwarding on the customer's router. The RTP port range (default value 10000 to 13999) must be forwarded to the IP address of your UCx Server. See Configure Port Forwarding for Remote Access for details.
For peer based SIP trunks (i.e. not registration based) or if remote SIP phones are used, you also need to port forward the SIP signaling port (default value 5060) on the customer's router. See Configure Port Forwarding for Remote Access for details.
Turn OFF SIP ALG on the customer router. See Deployment of UCx in a Network and Unexpected call failures and registration problems for details.
If there are remote Nortel phones connecting to the UCx, perform the following steps:
Configure the Public IP address of the UCx Server on the Nortel Settings page.
Port forward the Nortel phone signaling port (default value 7000) on the customer's router. See Configure Port Forwarding for Remote Access for details.