SIP/2.0 407 Proxy Authentication Required

The 407 Proxy Authentication Required response indicates that the phone must first authenticate itself with the proxy server. If received by phone, the phone may repeat the INVITE request with a suitable Proxy-Authorization field. This field should contain the authentication information of the user agent for the next outbound proxy or gateway.

Solutions

• Make sure username/password are correct
• Make sure you used username instead of user on the far server (e.g. other Asterisk servers) describing peer

Proxy Server to UA Authentication Call Flow

https://www.cisco.com/c/en/us/td/docs/ios/voice/sip/configuration/guide/12_4t/sip_12_4t_book/sip_cg-aaa.html

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Check also:

• SIP Error Codes