SIP response codes
SIP 488 Not Acceptable Here
Not Acceptable Here: the two sides have no media setup in common, most often no shared codec.
- Name
- Not Acceptable Here
- Class
- 4xx · Client error
- Defined in
- RFC 3261
- Produced from Q.850 causes
- 65, 70
When it happens
- The caller offers only codecs the callee has disabled (for example only G.729 or Opus against a G.711-only trunk).
- SRTP required on one side and not offered on the other.
- Video or T.38 fax offered to an endpoint that cannot handle it.
- A broken SDP (wrong address or port).
What to check
- Compare the codecs in the INVITE’s SDP with what the callee allows; enable a common codec, usually G.711 a-law/u-law.
- Make SRTP settings match, or enable transcoding on the PBX.
What the response looks like
SIP/2.0 488 Not Acceptable Here
Via: SIP/2.0/UDP 203.0.113.10:5060;branch=z9hG4bK776asdhds
From: <sip:101@pbx.example>;tag=1928301774
To: <sip:+15551234567@pbx.example>;tag=a6c85cf
Call-ID: a84b4c76e66710@203.0.113.10
CSeq: 2 INVITE
Content-Length: 0