System information

Troubleshooting ISDN
Book Title
17-388
Table 17-5 outlines the problems that might cause this symptom and describes solutions to those
problems.
Table 17-5 ISDN: No Communication End-to-End
ISDN: Second B Channel Does Not Come Up
Symptom: When using a second B channel as a backup connection to a single destination, the
second B channel does not come up.
Table 17-6 outlines the problems that might cause this symptom and describes solutions to those
problems.
Table 17-6 ISDN: Second B Channel Does Not Come Up
Possible Problem Solution
No default gateway
configured on end
systems
Step 1 Check the configuration of local and remote end systems. Make certain that end
systems are configured with a default-gateway specification.
Step 2 If an end systems is not configured with a default gateway, you must configure
one. For information on configuring your end system, refer to the vendor
documentation.
Step 3 If there is already a default gateway specification, make sure it points to the
correct address. The default gateway should point to a local router LAN
interface.
No route to remote
network
Step 1 Enter the show route privileged exec command for the particular protocol you
are using. For example, if you are using IP, enter show ip route ip-address.Ifthe
output says “Network not in table,” then there is no route to the remote network.
Step 2 If there are no routes to remote networks, you need to add static routes using the
appropriate command for the protocols you are running. For example, to
configure static IP routes, use the ip route global configuration command.
Step 3 You also need to configure floating static routes so there will be routes to the
remote networks after the primary link goes down.
For information on configuring floating static routes, refer to the Cisco IOS Wide-Area
Networking Configuration Guide and Wide-Area Networking Command Reference.
LAN media problem Make certain that your LAN media are functioning properly and that addressing and other
configurations are correct. For more information on troubleshooting LAN problems, refer
to the media troubleshooting chapter that covers the media type used in your network.
Hardware problem
Step 1 Check all hardware on end systems (workstations and servers). Replace any
damaged or malfunctioning hardware.
Step 2 Check all router hardware. Replace any damaged or malfunctioning router
hardware. For more information, refer to Chapter 3, “Troubleshooting Hardware
and Booting Problems.”