305 3xx Redirection RFC 3261
SIP 305 Use Proxy
The request must be sent through the proxy given in the Contact header.
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Common causes
- Policy that requires a specific outbound proxy.
How to fix it
- Configure the outbound proxy on the UA. Many UAs ignore 305 for security reasons.
Seeing 305 on calls through a router or firewall? Check that SIP ALG is disabled. It causes a surprising number of SIP errors. Read why.
About 3xx responses
The caller should try a different location to complete the request.