502 5xx Server error RFC 3261
SIP 502 Bad Gateway
A gateway or proxy got an invalid response from a downstream server.
Typical Q.850 / ISDN cause: 38 (Network out of order)
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Common causes
- The downstream carrier or server returned a bad response, or is broken.
How to fix it
- Escalate to the downstream provider with the Call-ID and timestamp.
Seeing 502 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.