505 5xx Server error RFC 3261
SIP 505 Version Not Supported
The server does not support the SIP protocol version in the request.
Typical Q.850 / ISDN cause: 79 (Service or option not implemented)
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Common causes
- Non-SIP/2.0 traffic or corrupted packets.
How to fix it
- Check for non-SIP traffic hitting the SIP port, or packet corruption.
Seeing 505 on calls through a router or firewall? Check that SIP ALG is disabled. It causes a surprising number of SIP errors. Read why.
About 5xx responses
The server failed to handle an apparently valid request.