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404
4xx Client error, RFC 3261

SIP 404 Not Found

SIP 404 Not Found means the server cannot find the number you dialled. Most often the number is in the wrong format, or it does not exist.

Who sends it
The SIP trunk
When
Placing the call (INVITE)
Retry?
Not until the number is corrected.
The caller hears
A failure tone or a message that the number is not recognised, usually without ringing.
PBXYour phone or PBX
SIPThe SIP trunksends 404
☎The called side
FIX

What causes 404, and how to fix it

On an outbound trunk, 404 almost always means the dialled number did not match any route, often because it was sent in the wrong format.

  1. 1
    Most common

    The number is dialled without the country code, or with a local trunk prefix such as a leading 0.

    Dial in international format: +, the country code, then the number without its leading 0. Check that your PBX dial plan does not add or strip digits.

  2. 2
    Most common

    The number does not exist or is no longer in service.

    Check the number with the person you are calling, or try it from a mobile.

  3. 3
    Sometimes

    The trunk has no route for that number range.

    Search the full number in the rate finder. If no route covers it, the call cannot be connected.

  4. 4
    Rare

    The PBX sends the call to the wrong address, so the server does not recognise the user part.

    Check that the outbound route sends the dialled number to the trunk, not to an internal extension.

LOG

What 404 looks like in a SIP log

SIP/2.0 404 Not Found

Capturing one: reading the SIP log.

SIP response
SIP/2.0 404 Not Found
Via: SIP/2.0/UDP 203.0.113.10:5060;branch=z9hG4bK-74bf9
Call-ID: [email protected]
≠

Not to be confused with

404, 484, 403 or 604?

484

Address Incomplete

The number is incomplete, too short to route. 404 means a full number was not found.

403

Forbidden

The number may exist, but you may not call it.

604

Does Not Exist Anywhere

The number does not exist anywhere. Some networks send 604 instead of 404.

FAQ

SIP 404 questions

Why do I get 404 for a number that works from my mobile?
Your mobile adds the right prefixes for you. A SIP trunk needs the full international format, so a local number without its country code is not found.
What number format should I dial?
E.164: a plus sign, the country code and the national number without its leading 0, for example +44 20 7946 0018. Up to 15 digits after the plus.

Not 404? Look up another code.

The full list: SIP response codes. 404 again and again? Check your SIP trunk configuration.

All SIP codesFind a fault by symptom