User guide

A-44 Cisco 2500 Series Access Server User Guide
Modems
Testing the Modem Connection
After connecting to the modem with a reverse Telnet, you need to test the connection. Send
the modem the at command to request its attention. It should respond with OK:
at
OK
If the modem does not reply to the at command, check the following:
1 Look at the output of the command show line 1. If it displays “no CTS” for the modem
hardware state, the modem is not connected, powered on, and waiting for data, or the
modem might not be configured for hardware flow control.
2 You may have problems with your cabling or modem configuration (echo or result codes
may be off). Try entering the command at to view the modem configuration, or entering
the command at&f to return to factory defaults.
Initiating, Suspending, and Terminating Telnet Sessions
The reverse Telnet must be terminated before the line can accept incoming calls. If you
don’t terminate the session, it will be indicated in the output of the command show users,
when it returns a modem state of ready if the line is still in use. If the line is no longer in
use, the output of the command show line value will return a state of idle.
Terminating the Telnet session requires first suspending it, then disconnecting it. To
suspend a Telnet session, enter the escape sequence Ctrl-Shift-6-x. You can then enter the
EXEC command disc to terminate the telnet session.
Note Ensure that you can reliably issue the escape sequence to suspend a Telnet session.
Some terminal emulator packages have difficulty sending the correct sequence,
Ctrl-Shift-6-x.
An example of how to use reverse Telnet to communicate with a modem follows:
Step 1 Initiate the session:
Router#telnet 172.16.1.10 2001
Trying 172.16.1.10, 2001 ... Open