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407
4xx Client error, RFC 3261

SIP 407 Proxy Authentication Required

SIP 407 Proxy Authentication Required means a proxy wants your username and password before it forwards the call. One 407 followed by the call going through is normal; repeated 407s mean the details are wrong.

Who sends it
The SIP trunk
When
Placing the call (INVITE)
Retry?
Your phone system retries on its own with the password. If 407 repeats, fix the details.
The caller hears
If authentication fails, a failure tone right after dialling.
PBXYour phone or PBX
SIPThe SIP trunksends 407
☎The called side
FIX

What causes 407, and how to fix it

407 is the proxy's version of 401. Trunks often challenge every INVITE this way. One 407 followed by a successful retry is normal; repeated 407s mean the credentials or realm are wrong.

  1. 1
    Most common

    The password used for outbound calls is wrong or missing, even though registration works.

    Check that the trunk uses the same username and password for calls as for registration. Some PBXs keep separate outbound credentials.

  2. 2
    Most common

    The authentication username for calls is empty or different from the SIP username.

    Put the SIP username in the auth username or from user field of the outbound trunk.

  3. 3
    Sometimes

    The PBX is set not to answer authentication challenges on calls.

    Enable outbound authentication on the trunk so the PBX answers the 407 with credentials.

  4. 4
    Rare

    Several trunks or contexts share one login with different settings.

    Make sure every route that uses this login has the same credentials.

LOG

What 407 looks like in a SIP log

SIP/2.0 407 Proxy Authentication Required

Capturing one: reading the SIP log.

SIP response
SIP/2.0 407 Proxy Authentication Required
Via: SIP/2.0/UDP 203.0.113.10:5060;branch=z9hG4bK-74bf9
Call-ID: [email protected]
Proxy-Authenticate: Digest realm="sip.linkedsip.com", nonce="9a41d07c", algorithm=MD5
≠

Not to be confused with

407, 401 or 403?

401

Unauthorized

The same digest challenge, sent by a registrar or the destination with WWW-Authenticate. 407 comes from a proxy with Proxy-Authenticate.

403

Forbidden

The server knows who you are and refuses the call.

FAQ

SIP 407 questions

What is the difference between SIP 401 and 407?
Both ask for credentials. 401 comes with a WWW-Authenticate header, usually from a registrar; 407 comes with Proxy-Authenticate from a proxy along the path. Your phone answers both the same way.
Is a SIP 407 an error?
Not on its own. Many trunks challenge every call. It only becomes a problem when the call keeps getting 407 instead of going through.

Not 407? Look up another code.

The full list: SIP response codes. 407 again and again? Check your SIP trunk configuration.

All SIP codesFind a fault by symptom