System information

Troubleshooting Dialin Connections 16-349
Troubleshooting Dialin Connections
Troubleshooting Dialin Connections
This section presents troubleshooting information for dialin connectivity problems. It describes
specific dialin connections symptoms, the problems that are likely to cause each symptom, and the
solutions to those problems.
Dialin: No Connectivity Between Modem and Router
Symptom: The connection between a modem and a Cisco access server or router does not work.
Attempts to initiate a reverse Telnet session to the modem have no result, or the user receives a
“connection refused by foreign host” message.
Note More specific symptoms for dialin connection problems are covered later in this chapter.
Table 16-2 outlines the problems that might cause this symptom and describes solutions to those
problems.
Table 16-2 Dialin: No Connectivity Between Modem and Router
Possible Causes Suggested Actions
Modem control is not enabled on the
access server or router
Step 1 Use the show line exec command on the access server or router. The
output for the auxiliary port should show inout or RIisCD in the
Modem column. This indicates that modem control is enabled on the
line of the access server or router.
For an explanation of show line output, see the “Using debug
Commands” section earlier in this chapter.
Step 2 Configure the line for modem control using the modem inout line
configuration command. Modem control is now enabled on the
access server.
Example:
The following example illustrates how to configure a line for both
incoming and outgoing calls:
line 5
modem inout
Modem control is not enabled on the
access server or router
Note: Be certain to use the modem inout command and not the
modem ri-is-cd command while the connectivity of the modem is in
question. The latter command allows the line to accept incoming
calls only. Outgoing calls will be refused, making it impossible to
establish a Telnet session with the modem to configure it. If you
want to enable the modem ri-is-cd command, do so only after you
are certain the modem is functioning correctly.
Incorrect cabling
Step 1 Check the cabling between the modem and the access server or
router. Confirm that the modem is connected to the auxiliary port on
the access server or router with a rolled RJ-45 cable and an MMOD
DB-25 adapter. This cabling configuration is recommended and
supported by Cisco for RJ-45 ports. (These connectors are typically
labelled “Modem.”)
Step 2 Use the show line exec command to verify that the cabling is correct.
See the explanation of the show line command output in the section
“Using debug Commands” earlier in this chapter.