System information

Troubleshooting ISDN Connections 17-393

ISDN: Line Disconnects Too Slowly

Symptom: ISDN connections are successfully established but idle connections do not disconnect

quickly enough.

Table 17-10 outlines the problems that might cause this symptom and describes solutions to those

problems.

Table 17-10 ISDN: Line Disconnects Too Slowly

Possible Problem Solution

No dialer hold-queue

command conﬁgured

Step 1 Use the show running-conﬁg privileged exec command to view the router

conﬁguration. Check for a dialer hold-queue interface conﬁguration

command entry.

Step 2 Conﬁgure the dialer hold-queue packets command on the outgoing

interface if it is not present already. This command allows interesting

outgoing packets to be queued until a modem connection is established.

The number of packets speciﬁed by this command should be less than 20.

Misconﬁgured dialer

idle-timeout command

Step 1 Use the show running-conﬁg privileged exec command to view the router

conﬁguration. Check for a dialer idle-timeout interface conﬁguration

command entry.

Syntax:

dialer idle-timeout seconds

This command speciﬁes the number of seconds before the router

disconnects an ISDN call due to lack of interesting trafﬁc as deﬁned by the

dialer-list command. Whenever an interesting packet is forwarded over

the ISDN line, the dial idle-timeout counter resets to 0 and begins

counting up again. When the counter reaches the speciﬁed value, the

router terminates the call. For proper operation, both routers should have

matching idle-timeout values. The default value is 120 seconds but can be

conﬁgured to a value between 1 and 2,147,483 seconds.

Step 2 Check the value speciﬁed by this command. If the ISDN line disconnects

too slowly when idle, the value is probably set too high.

Step 3 Decrease the value speciﬁed by the dialer idle-timeout command. This

forces connections to disconnect more quickly when they are idle.