Troubleshooting Incoming ISDN Call

Hello trainees , today we will learn how to troubleshoot an incoming ISDN call so you don't need to contact Cisco Systems' TAC (Technical Assistance Centre )

Use the command debug isdn q931 to watch the q931 signaling messages go back and forth while the router negotiates the ISDN connection. Here's an example output from a successful connection:

Router# debug isdn q931

RX <- SETUP pd = 8 callref = 0x06

 Bearer Capability i = 0x8890

 Channel ID i = 0x89

 Calling Party Number i = 0x0083, `5551234'

TX -> CONNECT pd = 8 callref = 0x86

RX <- CONNECT_ACK pd = 8 callref = 0x06

The SETUP message indicates that a connection is being initiated by the remote end. The call reference numbers are maintained as a pair. In this case, the call reference number for the incoming side of the connection is 0x06, while the call reference number of the outbound side of the connection is 0x86. The bearer capability (often referred to as the bearercap) tells the router what kind of call is coming in. In this case, the connection is type 0x8890. That value indicates "ISDN speed 64 kbps." If the bearercap had been 0x8090A2, it would have indicated "Speech/voice call u-law."

If no setup message was seen coming in, verify the correct number (try calling it manually, if it is voice-provisioned) and check the status of the ISDN interface (see Chapter 16, "Troubleshooting Dialup Connections"). If all that checks out, make sure that the call originator is making the correct call. Contact the telco to trace the call to see where it's being sent. If the connection is a long-distance one, try a different long-distance carrier using a 1010 long-distance code.

If the call coming in is an async modem call, make sure that the line is provisioned to allow voice calls.

If the call arrived but did not complete, look for a cause code (see Table 1). A successful completion is shown by a connect-ack being issued.

If this is an async modem call, move forward to the "Incoming Modem Call Troubleshooting" section.

At this point, the ISDN call is connected, but no data has been seen coming across the link. Use the command debug ppp negotiate to see whether any PPP traffic is coming across the line. If not, there may be a speed mismatch. To determine whether this is the case, use the show running-config privileged exec command to view the router configuration. Check the dialer map interface configuration command entries in the local and remote router. These entries should look similar to the following:

dialer map ip 131.108.2.5 speed 56 name C4000

For dialer profiles, a map class must be defined to set the speed. Note that, by default, ISDN interfaces attempt to use 64K communications speeds on each channel.

For detailed information on configuring dialer maps and profiles, refer to the Cisco IOS Dial Solutions Configuration Guide, Dial Solutions Command Reference, and Dial Solutions Quick Configuration Guide.

Getting valid PPP packets indicates that the link is up and working. Proceed to the section "Troubleshooting PPP."

Table 1

Hex Value	Cause	Explanation
81	Unallocated (unassigned) number	The ISDN number was sent to the switch in the correct format; however, the number is not assigned to any destination equipment.
90	Normal call clearing	Normal call clearing has occurred.
91	User busy	The called system acknowledges the connection request but is incapable of accepting the call because all B channels are in use.
92	No user responding	The connection cannot be completed because the destination does not respond to the call.
93	No answer from user (user alerted)	The destination responds to the connection request but fails to complete the connection within the prescribed time. The problem is at the remote end of the connection.
95	Call rejected	The destination is capable of accepting the call, but it rejected the call for an unknown reason.
9C	Invalid number format	The connection could not be established because the destination address was presented in an unrecognizable format or because the destination address was incomplete.
9F	Normal, unspecified	This reports the occurrence of a normal event when no standard cause applies. No action is required.
A2	No circuit/channel available	The connection cannot be established because no appropriate channel is available to take the call.
A6	Network out of order	The destination cannot be reached because the network is not functioning correctly, and the condition might last for an extended period of time. An immediate reconnect attempt will probably be unsuccessful.
AC	Requested circuit/channel not available	The remote equipment cannot provide the requested channel for an unknown reason. This might be a temporary problem.
B2	Requested facility not subscribed	The remote equipment supports the requested supplementary service by subscription only. This is frequently a reference to long-distance service.
B9	Bearer capability not authorized	The user requested a bearer capability that the network provides, but the user is not authorized to use it. This might be a subscription problem.
D8	Incompatible destination	This indicates that an attempt was made to connect to non-ISDN equipment—for example, to an analog line.
E0	Mandatory information element missing	The receiving equipment received a message that did not include one of the mandatory information elements. This is usually the result of a D-channel error. If this error occurs systematically, report it to your ISDN service provider.
E4	Invalid information element contents	The remote equipment received a message that includes invalid information in the information element. This is usually the result of a D-channel error.

now let's say you did all that and still didn't know how to fix the problem :( . In this time you have to call Cisco TAC but you need to collect some information and send it to them brfure you call them  . So what I want from you now is to go to this link Here and read the docemont then  let us know what are these things in the comment below for 2 extra mark .