System information

Troubleshooting ISDN
Book Title
17-378
• ISDN: Second B Channel Comes Up Too Late
• ISDN: Second B Channel Comes Up Too Early
• ISDN: Slow Performance
• ISDN: Line Disconnects Too Slowly
• ISDN: Line Disconnects Too Quickly
ISDN: Router Does Not Dial
Symptom: Router configured for ISDN does not dial.
Table 17-1 outlines the problems that might cause this symptom and describes solutions to those
problems.
Table 17-1 ISDN: Router Does Not Dial
Possible Problem Solution
Interface down
Step 1 Enter the show interfaces exec command to check the status of the ISDN interface.
Step 2 If the output of the show interfaces command indicates that the interface is
administratively down, bring the interface back up using the no shutdown interface
configuration command.
Step 3 If the interface or line protocol is down, check all cabling and connections.
Troubleshoot the hardware and the media. For more information, refer to Chapter 3,
“Troubleshooting Hardware and Booting Problems,” and Chapter 15,
“Troubleshooting Serial Line Problems.”
Missing or
misconfigured dialer
map commands
Step 1 Use the show running-config privileged exec command to view the router
configuration. Check whether there are dialer map interface configuration
commands configured for the protocols you are using.
Step 2 If there is not a dialer map configured for the protocol you are using, create a dialer
map for each protocol.
For example, if you want to configure a dialer map for IP, enter dialer map
commands similar to the following on the interface:
dialer map ip 172.16.20.2 name C4000 speed 56 broadcast
14155551234
dialer map ip 172.16.20.2 name C4000 speed 56 broadcast
14155556789
Step 3
If there are already dialer map commands present, make sure that the next hop
address is in the same subnet as the local interface address.
Step 4 If you want broadcast traffic to trigger the dialer, make sure that the broadcast
keyword is specified in your dialer map statements.
For detailed information on configuring dialer maps, refer to the Cisco IOS Wide-Area
Networking Configuration Guide and Wide-Area Networking Command Reference.