| Protocol | ims | Network | 5G and LTE |
|---|---|---|---|
| Spec | RFC 3261 / 3GPP TS 24.229 | Spec Section | SIP 405 Method Not Allowed failure response |
| Direction | IMS network -> UE | Message Type | SIP request-failure response |
| Full message name | IMS SIP 405 Method Not Allowed |
|---|---|
| Protocol | IMS |
| Technology | 5G and LTE |
| Common deployment | VoNR and VoLTE |
| Direction | IMS network -> UE |
| Interface | Gm with onward IMS routing |
| Signaling bearer / channel | IMS SIP signaling / Final request-failure response |
| Typical trigger | The far side or service rejects the method even though the target itself is valid. |
| Main purpose | Rejects the transaction because the method itself is not supported at that target. |
| Main specification | RFC 3261 / 3GPP TS 24.229, SIP 405 Method Not Allowed failure response |
| Release added | See specification history |
| Procedures where used | IMS Method Validation Failure |
405 Method Not Allowed means the target exists but does not allow the SIP method that was used.
Rejects the transaction because the method itself is not supported at that target.
405 means the target does not allow that SIP method.
Previous message(s): IMS SIP INFO, IMS SIP MESSAGE, IMS SIP REFER
Next message(s): Procedure stop or alternate method handling
Security context: Uses the same protected IMS signaling path as the original request.
SIP/2.0 405 Method Not Allowed
Via:
From:
To:
Call-ID:
CSeq:
Allow:
Content-Length: 0
This is SIP response syntax rather than ASN.1.
SIP/2.0 405 Method Not Allowed
Via: SIP/2.0/UDP ue.example.net;branch=z9hG4bK-info1
From: <sip:alice@example.net>;tag=mo1
To: <sip:bob@example.net>;tag=term1
Call-ID: call-001@example.net
CSeq: 5 INFO
Allow: INVITE, ACK, BYE
Content-Length: 0
| IE | Required | Description |
|---|---|---|
Status-Line | Yes | Shows the 405 failure code. |
Allow | Yes | Lists the SIP methods the target actually allows. |
Status-LineShows the 405 failure code.
Presence: Required
In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.
AllowLists the SIP methods the target actually allows.
Presence: Required
In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.
Likely cause: That target or service does not support the method used.
What to inspect: Check the Allow header and the exact method in the failed request.
Next step: Adjust the method or service feature instead of troubleshooting basic routing.
It means the target exists, but the SIP method used in the request is not allowed there.
Decode this message with the 3GPP Decoder, inspect the related message database, or open the matching call flow to see where this signaling step fits in the full procedure.