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voip guide

SIP 488 Not Acceptable Here

SIP 488 Not Acceptable Here usually means the endpoint understood the call request but could not accept the offered media. The answer is normally in the SDP offer and the endpoint policy.

What To Check First

  • Supported codecs in the SDP m=audio line.
  • Payload type mappings in rtpmap attributes.
  • SRTP or RTP policy mismatch.
  • DTMF method expectations such as RFC 2833 telephone-event.
  • IP version or address family mismatches.

Common Fixes

  • Enable a shared codec such as G.711, G.729, or Opus where appropriate.
  • Make sure SRTP requirements match on both sides.
  • Normalize SDP through an SBC when endpoints disagree.
  • Verify SIP ALG or firewall rewriting is not damaging SDP.

Use The Ladder

A SIP ladder diagram helps locate which endpoint sent the 488 and what offer it rejected. Pair it with the raw SDP so you can compare media capabilities instead of guessing.