Reference:ISDN Cause Codes

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H.323 (being based on Q.931 as ISDN is) uses the same cause codes as ISDN does. Such codes can be found in

  • traces
  • as well as in syslogs and
  • call detail records

Note that cause codes are coded differently in traces and syslogs. Here is how to extract cause codes from logs and traces and how they are coded.

Applies To

All innovaphone H.323 products

More Information

How to decode cause codes from traces

Within traces, you will find sequences similar to this:

0:0432:491:0 - TEI0.0 -> Q931.0 : LL_RECV_RESULT


08 02 80 02  45 08 02 82  81 1e 02 82  88            ....E........

if you have ticked the “trace” checkmark in the “interface configuration”.

Additionally, you will see something like:

0:0432:491:3 - R_CALL.7 -> RELAY.0 : SIG_DISC

       CAU = 82 81

if you have ticked the “trace” checkmark in the “protocol configuration”.

In the example, the cause code thus is 82 81.

The first byte (82) gives the Coding-standard and location. It is made up of: bit 8, 7, 6 and 5 usually 1000. Bit 4, 3, 2, 1 gives the location (that is, the entity generating the cause code). If bit 8 to 5 are unequal to 1000, the cause code is non-standard. The location is usually 0010, so that the second byte is usually 0x82 (10000010).

The second byte (81) contains the cause code within the lower 7 bit (1). So you need to clear the MSB to look up the cause code in the table below, using the “Cause (hex)” column. You may also look it up directly using the “Cause, bit 8 set to 1 (hex)” column.

There may be extraneous bytes giving further diagnostic information (Not described here and rarely used).

In the example case, the cause code thus is 0x1, which says “Unallocated number”.

How to decode cause codes from a CDR

CDRs (call detail records) show causes quite similar to the format described for traces, except that the size of the cause code information element is given and that the individual bytes are separated by underscores: cause=02_82_81

How to decode cause codes from a syslog

In a syslog, you will find cause codes for convenience already extracted from the respective information element and coded in decimal:

19700101-000325 CALL 0 B:Disc 32:ckl->00000009 GW1:21->PRI1:0000009: Cause: 1

You can look up the cause code directly in the table below using the “Cause (decimal)” column.

How to decode cause codes from a SIP message

In SIP messages, you may see header lines such as

Reason: Q.850;cause=18 

This indicates an ISDN cause code and it is given in decimal, so you can look it up in column 3 of the table below.

What if you don’t find the code

An innovaphone devices only rarely generates cause codes on its own. In normal operation, cause codes are received from the network and blindly output in traces, syslogs and cdr’s. Therefore, you might eventually see cause codes not listed in The table below. Consult the documentation of the cause code generating device to determine their meaning.

Q.931 ISDN Cause Codes

The following table shows the isdn errorcodes according to Q.931:

Errorcode (hex) Errorcode,
Bit 8 set to 1 (hex)
Errorcode (decimal) Meaning
0x1 0x81 1 Unallocated number
0x2 0x82 2 No route to specified transit network
0x3 0x83 3 No route to destination
0x6 0x86 6 Channel unacceptable
0x7 0x87 7 Call awarded and being delivered in an established channel
0x10 0x90 16 Normal call clearing
0x11 0x91 17 User busy
0x12 0x92 18 No user responding
0x13 0x93 19 No answer from user (user alerted)
0x15 0x95 21 Call rejected
0x16 0x96 22 Number changed
0x1A 0x9A 26 Non-selected user clearing
0x1B 0x9B 27 Destination out of order
0x1C 0x9C 28 Invalid number format
0x1D 0x9D 29 Facility rejected
0x1E 0x9E 30 Response to STATUS ENQUIRY
0x1F 0x9F 31 Normal, unspecified
0x22 0xA2 34 No circuit/channel available
0x26 0xA6 38 Network out of order
0x29 0xA9 41 Temporary failure
0x2A 0xAA 42 Switching equipment congestion
0x2B 0xAB 43 Access information discarded
0x2C 0xAC 44 Requested circuit/channel not available
0x2D 0xAD 47 Resources unavailable, unspecified
0x31 0xB1 49 Quality of service unavailable
0x32 0xB2 50 Requested facility not subscribed
0x34 0xB4 52 Outgoing calls barred
0x35 0xB5 53 Outgoing calls barred within CUG
0x39 0xB9 57 Bearer capability not authorised
0x3A 0xBA 58 Bearer capability not presently available
0x3F 0xBF 63 Service or option not available, unspecified
0x41 0xC1 65 Bearer capability not implemented
0x42 0xC2 66 Channel type not implemented
0x45 0xC5 69 Requested facility not implemented
0x46 0xC6 70 Only restricted digital information bearer capability is available
0x4F 0xCF 79 Service or option not implemented, unspecified
0x51 0xD1 81 Invalid call reference value
0x52 0xD2 82 Identified channel does not exist
0x53 0xD3 83 A suspended call exists, but this call identity does not
0x54 0xD4 84 Call identity in use
0x55 0xD5 85 No call suspended
0x56 0xD6 86 Call having the requested call identity has been cleared
0x58 0xD8 88 Incompatible destination
0x5B 0xDB 91 Invalid transit network selection
0x5F 0xDF 95 Invalid message, unspecified
0x60 0xE0 96 Mandatory information element missing
0x61 0xE1 97 Message type non-existent or not implemented
0x62 0xE2 98 Message not compatible with call state
0x63 0xE3 99 Information element non-existent or nor implemented
0x64 0xE4 100 Invalid information element contents
0x65 0xE5 101 Message not compatible with call state
0x66 0xE6 102 Recovery on timer expiry
0x6F 0xEF 111 Protocol error, unspecified
0x7F 0xFF 127 Interworking, unspecified

Display messages on IP2xx

Errorcode German view English view français view
1 Unbekannte Nummer number unknown Numéro inconnu
2 Keine Verb. zum Netz no networks access Pas de liais. réseau
3 Keine Verb. zum Ziel no route to dest. Pas de liais. dest.
4 sende spez. Inf. Ton send spec. inf. tone Tonalité spéciale
5 falscher Carrier-Code misdial. trunk prefix Accès réseau erroné
6 Kanal nicht akzept. Channel unacceptable Canal non dispo
7 Gespräch schon zug. call being delivered Appel en cours achem.
16 Wahl abgebrochen Error while dialling Délai numéro. dépassé
17 besetzt subscriber busy Occupé
18 Ziel nicht erreicht no user responding Aucun poste atteint
19 keine Antwort no answer Pas de réponse
20 nicht erreichbar subscriber absent Pas de réponse
21 abgelehnt call rejected Appel rejeté
22 Nummer geändert number changed Numéro modifié
27 Ziel nicht bereit dest. not ready Destin. non dispo.
28 Nr. Unvollst./ungült. incomplete/invalid no Numéro erroné
29 Dienst abgelehnt service rejected Service refusé
30 Keine Antw. auf ST. no response to STATE STATUT:pas de réponse
31 Wahl abgebrochen Error while dialling Délai numéro. dépassé
34 Kein Kanal verfügbar no channel available Acun canal dispo
38 Netz nicht bereit network not ready Réseau indisponible
41 temporärer Netzfehl. temporary failure Dérangement tempor.
42 Netz überlastet network overload Réseau encombré
43 Netzinfo gelöscht access info discarded Info réseau effacée
44 Kanal nicht frei channel not free Canal non libre
47 Netz überlastet network overload. Réseau encombré
49 Dienst-Art n. mögl. service unavail. Service non dispo.
50 Dienst n. bekannt service unknown Service inconnu
52 Nummer gesperrt! Number barred! Numéro verrouillé!
53 ausg. gesperrt - CUG outgoing barred - CUG Appel externe interdi
54 eingehend gesperrt incoming barred Appel entrant interdi
55 eing. gesperrt - CUG incoming barred - CUG Appel entrant interdi
57 Dienst unzulässig service unauthorised Service non autorisé
58 Dienst z.Zt n. mögl. service not available Service actu. indisp.
62 ausg. Daten inkosist inconsist. autg. data Accés ext. imprécis
63 Dienst nicht bekannt service unknown Service inconnu
65 Basis-Dienst n. impl b.-service not impl. Service non implém.
66 Kanal-Art nicht impl ch. type not impl. Type canal non impl.
69 Dienst nicht impl. service not impl. Service non implém.
70 nur eingesch. Dienst only restr. service Serv. restreint uniq.
79 Dienst nicht impl. service not impl. Service non implém.
81 falsche Call-Ref invalid call-ref Réf. d'appel erronée
82 falscher Kanal wrong channel Canal inexistant
83 falscher Code wrong code Code erroné
84 Code wird benutzt code is in use Code utilisé
85 keine Verb. geparkt co call on hold Pas de com. en att.
86 Geparkte Verb. ausg. call has been cleared Commun. acceptée
87 nicht Mitglied in CUG user not a CUG member Util. non membre CUG
88 Ziel ist inkompat. incompatible dest. Destin. incompatible
90 CUG existiert nicht non existent CUG CUG inexistant
91 Ungültiges Netz invalid network Choix réseau incor.
95 Fehlerhafte Message invalid message Message incorrect
96 Info-Element fehlt info element missing Elém. Info manquant
97 Message nicht impl. message not impl. Message non implém.
98 Message nicht komp. message not comp. Message incompatible
99 Info nicht bekannt info unknown Elém.Info inconnu
100 Fehlerhafte Info wrong info Info incorrecte
101 Falscher Call-Status wrong call status Statut appel erroné
102 Abbruch nach Timeout timeout Délai dépassé
103 falscher Parameter wrong parameter Paramètre inexistant
110 Daten inkonsistent inconsistency in data Données inconstantes
111 Protokoll-Fehler protocol error Erreur protocole
127 Interworking Fehler interworking error Erreur fonctionnement

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