--- title: "SIP 405 Method Not Allowed" url: "https://enfonica.com/help/sip-errors/405-method-not-allowed" summary: "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." type: error audience: everyone products: ["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" --- # 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 First check the [Enfonica status page](https://enfonica.status.io/) for a known incident. ## A phone, softphone, or ATA can't register What you see: `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 **To 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. **To fix it**, 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: - **3CX**. Suits most businesses. To learn how, see [Connect 3CX to Cloud SIP](https://enfonica.com/help/3cx/connect-3cx-cloud-sip). - **FreePBX, FusionPBX, or Asterisk**. Open source. FusionPBX is built for many tenants on one server, which suits residential phone services with one ATA per household. To learn how, see [Connect FreePBX, FusionPBX, or Asterisk to Cloud SIP](https://enfonica.com/help/sip-trunking/connect-freepbx). - **Microsoft Teams Direct Routing**. Suits teams that already call from Teams. To learn how, see [Connect Microsoft Teams Direct Routing to Enfonica](https://enfonica.com/help/teams-direct-routing/connect-teams-direct-routing). 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 **To 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`. **To fix it**, 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](https://enfonica.com/help/sip-trunking/load-balancing-failover). ## Call transfers fail with 405 What you see: `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 **To 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. **To fix it**, 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](https://enfonica.com/help/sip-trunking/connect-ai-voice-agent). ## Other SIP requests fail with 405 What you see: `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 **To check**, look in the SIP trace for a request other than those five, followed by `405 Method not allowed`. **To fix it**, 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](https://enfonica.com/blog/how-to-test-sip-connectivity-using-sipsak/). For other errors on outbound calls, see [Outbound calls aren't going through](https://enfonica.com/help/call-troubleshooting/outbound-calls-fail). ## 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](https://enfonica.com/contact-support?article=%2Fhelp%2Fsip-errors%2F405-method-not-allowed&topic=call-fault) ## Related - [Outbound calls aren't going through](https://enfonica.com/help/call-troubleshooting/outbound-calls-fail.md) - [Connect your PBX to Cloud SIP](https://enfonica.com/help/sip-trunking/connect-pbx-to-cloud-sip.md) - [Connect 3CX to Cloud SIP](https://enfonica.com/help/3cx/connect-3cx-cloud-sip.md) - [Connect FreePBX, FusionPBX, or Asterisk to Cloud SIP](https://enfonica.com/help/sip-trunking/connect-freepbx.md) - [Connect an AI voice agent to Cloud SIP](https://enfonica.com/help/sip-trunking/connect-ai-voice-agent.md) - [Send incoming calls to more than one PBX or site, with failover](https://enfonica.com/help/sip-trunking/load-balancing-failover.md) --- Web version: https://enfonica.com/help/sip-errors/405-method-not-allowed