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The Cisco Unified Communication Manager (CUCM) does not allow multiple endpoints to register with same IP Port addresses. Any subsequent registration that uses same IP Port is rejected with 405 response code. SBC overcomes this with the ability to use different ports for each new registration on egress side when registering with CUCM using the flag usePortRangeFlag.

When this flag is enabled, SBC egresses the SIP REGISTER message via a new port for each REGISTER message. This feature uses the media port range configured on trunk group and at the global level for to open the port. SBC maintains the connection IDs based on SipSigPort ID, Protocol, IP Address Type and IP Address. SBC sends the message using a different connection ID for UDP. SBC uses the same connection ID for sending out the subsequent messages from the corresponding registered user.

Some salient points to note for this feature:

• SBC uses the independent media port range per IPTG if configured.

• SBC uses the system wide media port range if no independent media port range is configured per IPTG.

• SBC uses a different port from this port range for each unique new egress registration towards the trunk group. Any de-registration shall free the corresponding port for re-use by another registration or media port requirement.