Asterisk Hangup Cause

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Hangup Cause Mappings

Asterisk Hangup Cause Code Mappings:

Disconnect causes

Asterisk Value ISDN Cause codes (Q.850 & Q.931 unless specified) MFC/R2 SIP/PJSIP Motif
AST_CAUSE_NO_ROUTE_TRANSIT_NET 2. No route to specified transmit network      
AST_CAUSE_NO_ROUTE_DESTINATION 3. No route to destination   420  
AST_CAUSE_MISDIALLED_TRUNK_PREFIX 5. Misdialled trunk prefix (national use)      
AST_CAUSE_CHANNEL_UNACCEPTABLE 6. Channel unacceptable      
AST_CAUSE_CALL_AWARDED_DELIVERED 7. Call awarded and being delivered in an established channel      
AST_CAUSE_NUMBER_PORTED_NOT_HERE 14. QoR: ported number      
AST_CAUSE_USER_BUSY 17. User busy OR2_CAUSE_BUSY_NUMBER 486, 600 busy
AST_CAUSE_NO_USER_RESPONSE 18. No user responding   408 expired
AST_CAUSE_NO_ANSWER 19. No answer from user (user alerted) OR2_CAUSE_NO_ANSWER 480, 483  
AST_CAUSE_CALL_REJECTED 21. Call Rejected   401, 403, 407, 603 cancel, decline
AST_CAUSE_NUMBER_CHANGED 22. Number changed   410  
AST_CAUSE_REDIRECTED_TO_NEW_DESTINATION 23. Redirected to new destination      
AST_CAUSE_ANSWERED_ELSEWHERE 26. Non-selected user clearing (ASTERISK-15057)      
AST_CAUSE_INVALID_NUMBER_FORMAT 28. Invalid number format   484  
AST_CAUSE_FACILITY_REJECTED 29. Facility rejected   501  
AST_CAUSE_NORMAL_UNSPECIFIED 31. Normal, unspecified      
AST_CAUSE_NORMAL_CIRCUIT_CONGESTION 34. No circuit/channel available (Note tdat we've called tdis "Circuit/channel congestion" for a while which can cause confusion witd code 42) OR2_CAUSE_NETWORK_CONGESTION   general-error
AST_CAUSE_NETWORK_OUT_OF_ORDER 38. Network out of order   500  
AST_CAUSE_NORMAL_TEMPORARY_FAILURE 41. Temporary failure   409  
AST_CAUSE_SWITCH_CONGESTION 42. Switching equipment congestion   5xx failed-application
AST_CAUSE_ACCESS_INFO_DISCARDED 43. Access information discarded      
AST_CAUSE_REQUESTED_CHAN_UNAVAIL 44. Requested circuit/channel not available      
AST_CAUSE_FACILITY_NOT_SUBSCRIBED 50. Requested facility not subscribed      
AST_CAUSE_OUTGOING_CALL_BARRED 52. Outgoing call barred      
AST_CAUSE_INCOMING_CALL_BARRED 54. Incoming call barred      
AST_CAUSE_BEARERCAPABILITY_NOTAUtd 57. Bearer capability not autdorized      
AST_CAUSE_BEARERCAPABILITY_NOTAVAIL 58. Bearer capability not presently available   488, 606 incompatible-parameters, media-error, unsupported-applications
AST_CAUSE_BEARERCAPABILITY_NOTIMPL 65. Bearer capability not implemented      
AST_CAUSE_CHAN_NOT_IMPLEMENTED 66. Channel type not implemented      
AST_CAUSE_FACILITY_NOT_IMPLEMENTED 69. Requested facility not implemented     unsupported-transports
AST_CAUSE_INVALID_CALL_REFERENCE 81. Invalid call reference value      
AST_CAUSE_INCOMPATIBLE_DESTINATION 88. Incompatible destination      
AST_CAUSE_INVALID_MSG_UNSPECIFIED 95. Invalid message unspecified      
AST_CAUSE_MANDATORY_IE_MISSING 96. Mandatory information element is missing      
AST_CAUSE_MESSAGE_TYPE_NONEXIST 97. Message type non-existent or not implemented      
AST_CAUSE_WRONG_MESSAGE 98. Message not compatible witd call state or message type non-existent or not implemented      
AST_CAUSE_IE_NONEXIST 99. Information element nonexistent or not implemented      
AST_CAUSE_INVALID_IE_CONTENTS 100. Invalid information element contents      
AST_CAUSE_WRONG_CALL_STATE 101. Message not compatible witd call state      
AST_CAUSE_RECOVERY_ON_TIMER_EXPIRE 102. Recover on timer expiry   504 timeout
AST_CAUSE_PROTOCOL_ERROR 111. Protocol error, unspecified     failed-transport, security-error
AST_CAUSE_INTERWORKING 127. Interworking, unspecified   4xx, 505, 6xx connectivity-error
AST_CAUSE_MANDATORY_IE_LENGtd_ERROR ? Mandatory IE lengtd error      
AST_CAUSE_PRE_EMPTED ISUP - 8. Preemption      
  1. Unallocated (unassigned) number
  404, 485, 604  

ITU-T Recommendation Q.931' is the ITU standard ISDN connection control signalling protocol, forming part of Digital Subscriber Signalling System No. 1.[1] Unlike connectionless systems like UDP, ISDN is connection oriented and uses explicit signalling to manage call state: Q.931. Q.931 typically does not carry user data. Q.931 does not have a direct equivalent in the Internet Protocol stack, but can be compared to SIP. Q.931 does not provide flow control or perform retransmission, since the underlying layers are assumed to be reliable and the circuit-oriented nature of ISDN allocates bandwidth in fixed increments of 64 kbit/s. Amongst other things, Q.931 manages connection setup and breakdown. Like TCP, Q.931 documents both the protocol itself and a protocol state machine.

Q.931 was designed for ISDN call establishment, maintenance, and release of network connections between two DTEs on the ISDN D channel. Q.931 has more recently been used as part of the VoIP H.323 protocol stack (see H.225.0) and in modified form in some mobile phone transmission systems[2] and in ATM.

A Q.931 frame contains the following elements:

  • Protocol discriminator (PD) – Specifies which signaling protocol is used for the connection (e.g. PD=8 for DSS1)
  • Call reference value (CR) – Addresses different connections which can exist simultaneously. The value is valid only during the actual time period of the connection
  • Message type (MT) – Specifies the type of a layer 3 message out of the Q.931-defined Message type set for call control (e.g. SETUP). There are messages defined for the call setup, the call release and the control of call features.
  • Information elements (IE) – Specify further information which is associated to the actual message. An IE contains the IE name (e.g. bearer capability), their length and a variable field of contents.

Message examples

Messages typically control or report the status of connections. For example:

  • SETUP (indicating the establishment of a connection)
  • CALL PROCEEDING (indicating that the call is being processed by the destination terminal)
  • ALERTING (tells the calling party that the destination terminal is ringing)
  • CONNECT (sent back to the calling party indicating that the intended destination has answered the call)
  • DISCONNECT (sent to indicate a request to terminate the connection, by the end that seeks to terminate)
  • RELEASE (sent in response to the disconnect request indicating that the call is to be terminated).
  • RELEASE COMPLETE (sent by the receiver of the release to complete the handshake).

Disconnect causes

Hex Decimal Cause
0x1 1 Unallocated or unassigned number
0x2 2 No route to specified transit network (Transit Network Identity)
0x3 3 No route to destination
0x4 4 Send special information tone
0x5 5 Misdialled trunk prefix
0x6 6 Channel unacceptable
0x7 7 Call awarded and being delivered in an established channel
0x8 8 Prefix 0 dialed but not allowed
0x9 9 Prefix 1 dialed but not allowed
0xA 10 Prefix 1 not dialed but required
0xB 11 More digits received than allowed, call is proceeding
0x10 16 Normal call clearing
0x11 17 User busy
0x12 18 No user responding
0x13 19 T.301 expired: – User Alerted, No answer from user
0x15 21 Call rejected
0x16 22 Number changed to number in diagnostic field.
0x17 23 Reverse charging rejected
0x18 24 Call suspended
0x19 25 Call resumed
0x1A 26 Non-selected user clearing
0x1B 27 Destination out of order
0x1C 28 Invalid number format or incomplete address
0x1D 29 EKTS facility rejected by network
0x1E 30 Response to STATUS ENQUIRY
0x1F 31 Normal, unspecified
0x21 33 Circuit out of order
0x22 34 No circuit/channel available
0x23 35 Destination unattainable
0x24 36 Out of order
0x25 37 Degraded service
0x26 38 Network out of order
0x27 39 Transit delay range cannot be achieved
0x28 40 Throughput range cannot be achieved
0x29 41 Temporary failure
0x2A 42 Switching equipment congestion
0x2B 43 Access information discarded
0x2C 44 Requested circuit channel not available
0x2D 45 Preempted
0x2E 46 Precedence call blocked
0x2F 47 Resource unavailable, unspecified
0x31 49 Quality of service unavailable
0x32 50 Requested facility not subscribed
0x33 51 Reverse charging not allowed
0x34 52 Outgoing calls barred
0x35 53 Outgoing calls barred within CUG
0x36 54 Incoming calls barred
0x37 55 Incoming calls barred within CUG
0x38 56 Call waiting not subscribed
0x39 57 Bearer capability not authorized
0x3A 58 Bearer capability not presently available
0x3F 63 Service or option not available, unspecified
0x41 65 Bearer service not implemented
0x42 66 Channel type not implemented
0x43 67 Transit network selection not implemented
0x44 68 Message not implemented
0x45 69 Requested facility not implemented
0x46 70 Only restricted digital information bearer capability is available
0x4F 79 Service or option not implemented, unspecified
0x51 81 Invalid call reference value
0x52 82 Identified channel does not exist
0x53 83 A suspended call exists, but this call identity does not
0x54 84 Call identity in use
0x55 85 No call suspended
0x56 86 Call having the requested call identity has been cleared
0x57 87 Called user not member of CUG
0x58 88 Incompatible destination
0x59 89 Non-existent abbreviated address entry
0x5A 90 Destination address missing, and direct call not subscribed
0x5B 91 Invalid transit network selection (national use)
0x5C 92 Invalid facility parameter 93 Mandatory information element is missing
0x5D 93 Message type non-existent or not implemented
0x5F 95 Invalid message, unspecified
0x60 96 Mandatory information element is missing
0x61 97 Message type non-existent or not implemented
0x62 98 Message not compatible with call state or message type non-existent or not implemented
0x63 99 Information element nonexistent or not implemented
0x64 100 Invalid information element contents
0x65 101 Message not compatible with call state
0x66 102 Recovery on timer expiry
0x67 103 Parameter non-existent or not implemented – passed on
0x6F 111 Protocol error, unspecified
0x7F 127 Internetworking, unspecified
0x80+ 128 or


Proprietary diagnostic code (not necessarily bad). Typically used to pass proprietary control or maintenance messages between multiplexers.


Q.2931[3] is a modified and extended variant of Q.931 for use on "B-ISDN" or ATM networks. Q.2931 fulfils a purpose within BISDN similar to that of Q.931 in ISDN. Whist ISDN allocates bandwidth in fixed 64k increments, B-ISDN/ATM incorporates an elaborate traffic management scheme, allowing precise specification of virtual circuit traffic parameters such as peak and mean bandwidth, jitter, cell loss ratio and so on. In order that ATM switches can manage bandwidth allocation in the network, encodings to express these parameters were added in Q.2931.[4]

Unlike Q.931, although Q.2931 was implemented by many switch manufacturers, it was never widely deployed.


  1. ITU-T Recommendation Q.931 Digital subscriber Signalling System No. 1: ISDN user-network interface layer 3 specification for basic call control
  2. such as in GSM, where it is used for circuit switched call control between UE and MSC
  3. ITU-T Recommendation Q.2931 Digital Subscriber Signalling System No. 2 – User-Network Interface (UNI) layer 3 specification for basic call/connection control
  4. for example, see the Extended Quality of Service or eQoS Information Element, which can indicate many quality of service parameters