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SIP Response Codes

Some SIP phones and all PBXs display errors or a prompts using the SIP Response codes, this document contains a list of SIP codes which can help you diagnose problems. 

SIP response codes, class 1

The 1xx response codes are provisional messages sent indicating call progress. 

  • 100 Trying
  • 180 Ringing
  • 181 Call Is Being Forwarded
  • 182 Queued
  • 183 Session Progress

SIP Response codes: class 2

The 2xx class of response codes indicates a success. 

  • 200 OK

SIP response codes, class 3

The 3xx response codes indicate a redirection of the call. 

  • 300 Multiple Choices
  • 301 Moved Permanently
  • 302 Moved Temporarily
  • 305 Use Proxy
  • 380 Alternative Service

SIP responses, class 4

The 4xx response codes indicate request failures 

  • 400 Bad Request
  • 401 Unauthorized: Used only by registrars. Proxys should use proxy authorization 407
  • 402 Payment Required (Reserved for future use)
  • 403 Forbidden
  • 403 - Insufficient funds ( often related to the balance on the account or the Fraud control settings for the destination number)
  • 404 Not Found: User not found ( Typically the PBX will deliver when an inbound route is not set-up for the DID)
  • 405 Method Not Allowed
  • 406 Not Acceptable
  • 407 Proxy Authentication Required
  • 408 Request Timeout: Couldn't find the user in time
  • 409 Conflict
  • 410 Gone: The user existed once but is no longer available
  • 413 Request Entity Too Large
  • 414 Request-URI Too Long
  • 415 Unsupported Media Type
  • 416 Unsupported URI Scheme
  • 420 Bad Extension: Bad SIP Protocol Extension used, not understood by the server
  • 421 Extension Required
  • 422 Session Interval Too Small
  • 423 Interval Too Brief
  • 480 Temporarily Unavailable
  • 481 Call/Transaction Does Not Exist
  • 482 Loop Detected
  • 483 Too Many Hops
  • 484 Address Incomplete
  • 485 Ambiguous
  • 486 Busy Here
  • 487 Request Terminated
  • 488 Not Acceptable Here
  • 491 Request Pending
  • 493 Undecipherable: Could not decrypt S/MIME body part

SIP responses, class 5

The 5xx response codes indicate server failures. 

  • 500 Server Internal Error
  • 501 Not Implemented: The SIP request method is not implemented here
  • 502 Bad Gateway
  • 503 Service Unavailable
  • 504 Server Time-out
  • 505 Version Not Supported: The server does not support this version of the SIP protocol
  • 513 Message Too Large

SIP response codes, class 6

The 6xxx response codes represent global failures. 

  • 600 Busy Everywhere
  • 603 Decline
  • 604 Does Not Exist Anywhere
  • 606 Not Acceptable
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