SIP 405 Method Not Allowed
The far end recognises the address but will not accept that kind of request. In practice this shows up when a feature such as attended transfer or message waiting is used against a device that does not allow it.
What SIP 405 Method Not Allowed actually means
The method in the request is understood but not allowed for that address, and the response lists the methods that are permitted. That list is the useful part, because it tells you exactly what the device will accept instead of guessing.
What causes SIP 405 on a business phone system
- Transfer is attempted where the far end does not support itSome trunks and gateways refuse the request used for attended transfer, so transfers fail while ordinary calls work.
- A feature message is sent to a device that disallows itMessage waiting indication, presence updates and in-call information messages can all be refused by devices not configured for them.
How to fix SIP 405
- Read the permitted methods from the responseThe Allow header lists what the device will accept, which tells you immediately whether the feature is possible at all.
- Switch the transfer method on the PBXWhere attended transfer is refused, configuring the system to bridge the call itself rather than hand it off usually resolves it.
Fixing the underlying problem
This page explains the code. These guides walk through the fix in detail.
Questions about SIP 405
Why do transfers fail with SIP 405?
Related SIP response codes
Source. SIP 405 Method Not Allowed is defined in RFC 3261 section 21.4.6 and registered in the IANA SIP Parameters — Response Codes. The causes and fixes above are drawn from our own experience supporting UK business phone systems.