Error reference

SIP 405 Method Not Allowed

Short answer

Cloud SIP is a SIP trunk. It accepts calls, but not SIP registration or call transfers by SIP REFER, and it answers both with 405 Method not allowed. Turn registration off on your trunk, connect phones to a PBX, and use transfers that your PBX or platform bridges itself.

Applies to
Cloud SIP
Works with
Any SIP PBX or SBC, SIP phones, softphones and ATAs
Who can do this
Whoever manages your PBX, phones or voice platform

Check for a known incident first. If there is one, we're already working on it, and there's nothing to change on your side.

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On this page
  1. What are you seeing?
  2. A phone, softphone, or ATA can't register
  3. Call transfers fail with 405
  4. Other SIP requests fail with 405
  5. Questions
  6. What to send us
  7. Related

What are you seeing?

A phone, softphone, or ATA can't register

SIP/2.0 405 Method not allowed

Cloud SIP connects a PBX (a phone system) to the phone network. It isn't a registrar, so it doesn't accept SIP registration (REGISTER) on any SIP domain. No Console or API setting turns registration on. A device that tries to register gets 405 Method not allowed, or sometimes no response at all.

The device connects directly to the trunk

Check

Look at the device's account settings. This is the cause if a desk phone, softphone, or ATA (analog telephone adapter) has an account that points at your SIP domain, for example example.sip.enfonica.com, with registration turned on.

Fix

Register the device to a PBX, and connect the PBX to Cloud SIP. The PBX can be cloud-hosted, so nothing needs to be on site. These PBXs work with Cloud SIP:

A softphone with registration turned off can sometimes make outgoing calls using IP authentication. Incoming calls can't reach it, though, so we don't support this setup.

Your PBX's trunk is set to register

Check

Look for a registration error in your PBX. 3CX, for example, shows Call or Registration to example.sip.enfonica.com has failed with 405 Method not allowed.

Fix

Turn registration off on the trunk. If you use a username and password, keep them. Your PBX sends them with each call when Cloud SIP asks for them.

  • In 3CX, set Type of authentication to Do not require - IP based, and leave the username and password in place. Calls are still authenticated.
  • In Asterisk and FreePBX, use a PJSIP trunk with outbound authentication and no registration.

Without registration, Cloud SIP needs to be told where your PBX is so that it can send incoming calls there. Adding a username and password doesn't change that. Point your numbers at your PBX's public IP address or DNS name, usually through a load balancer. To learn how, see Send incoming calls to more than one PBX or site, with failover.

Call transfers fail with 405

SIP/2.0 405 Method not allowed

Some transfers work by sending SIP REFER, which asks the other side of the call to make the new call itself. Cloud SIP doesn't accept REFER, so it refuses the transfer with a 405.

Your PBX or platform transfers calls with REFER

Check

Look in the SIP trace for a REFER request followed by 405 Method not allowed. It's most common with AI voice agents and hosted call platforms.

Fix

Select a transfer type that your PBX or platform completes itself. It makes a new call to the transfer destination and joins the two calls together. AI voice agent platforms often call this a conference transfer.

The new call goes out through your trunk like any other outgoing call, so it needs a valid caller ID. For the settings, see Connect an AI voice agent to Cloud SIP.

Other SIP requests fail with 405

Allow: INVITE, ACK, OPTIONS, CANCEL, BYE

Cloud SIP accepts the five requests that a SIP trunk needs to make, answer, and end calls. It lists them in the Allow header of its responses. Any other request, such as SUBSCRIBE, NOTIFY, MESSAGE, INFO, or UPDATE, gets a 405.

Your PBX uses a SIP feature over the trunk that the trunk doesn't offer

Check

Look in the SIP trace for a request other than those five, followed by 405 Method not allowed.

Fix

Turn that feature off on the Enfonica trunk in your PBX. Features such as presence and busy lamp field (BLF) work between your phones and your PBX, and don't need the trunk.

Questions

Can Enfonica turn on registration for my SIP domain?

No. Registration isn't available on any SIP domain, and there's no setting for it. Connect your phones to a PBX, and connect the PBX to Cloud SIP.

My PBX has a changing IP address or sits behind NAT. How do incoming calls reach it?

Give your PBX a dynamic DNS name that follows its IP address, and use that name in the load balancer that sends calls to it. For outgoing calls, authenticate with a username and password, because an IP access control list can't follow an address that changes.

Can I check that the trunk is reachable without registering?

Yes. Send a SIP OPTIONS request to your SIP domain, and Cloud SIP answers 200 Keepalive. Many PBXs do this on their own to monitor the trunk. To try it by hand, see How to test SIP connectivity using sipsak.

For other errors on outbound calls, see Outbound calls aren't going through.

What to send us

Include these and we can find the call straight away.

  • The number that made the call and the number it called, in full international format (for example +61255501234).
  • The date and time of the call, with your timezone.
  • Whether the call was inbound or outbound.
  • The call ID, if the Console shows the call.
  • What happened: an error message, silence, a busy tone or a dropped call.
Contact support

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