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3xx Redirect Support is enabled by default on the IMG and is configurable with the SIP Profile (SGP) on a per gateway basis - see IMG 1010 - SIP Profile - 10.5.3 and IMG 1010 - SIP Redirect Server Support
300 Multiple Choices
The address in the request resolved to several choices, each with its own specific location, and the user (or UA) can select a preferred communication end point and redirect its request to that location.
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