CCIE Practical Studies: Security (CCIE Self-Study)

ISDN Cause Code Fields

Whenever you start an ISDN debug session, one of the first things you notice is that any failure or error appears as a line of gibberish. This gibberish is actually the ISDN cause code. It is composed of fields that are normally displayed in the following format:

I = 0x y1 y2 z1 z2 [a1 a2]

Table C-2 describes these fields to help you decode these messages.

Table C-2. ISDN Cause Code Fields

Cause Code Field	Value Description
0x	Indicates that the values that follow are in hexadecimal.
y1	8— ITU-T standard coding.
y2	0— User 1— Private network serving local user 2— Public network serving local user 3— Transit network 4— Public network serving remote user 5— Private network serving local user 6— International network A— Network beyond ...