Cisco Systems DC-145 User Manual
Configuring and Managing External Modems
This chapter describes how to configure externally connected modems. These tasks are presented in the
following main sections:
• External Modems on Low-End Access Servers
• Automatically Configuring an External Modem
• Manually Configuring an External Modem
• Supporting Dial-In Modems
• Testing the Modem Connection
• Managing Telnet Sessions
• Modem Troubleshooting Tips
• Checking Other Modem Settings
To identify the hardware platform or software image information associated with a feature, use the
Feature Navigator on Cisco.com to search for information about the feature or refer to the software
release notes for a specific release. For more information, see the “Identifying Supported Platforms”
section in the “Using Cisco IOS Software” chapter.
For a complete description of the modem support commands in this chapter, refer to the Cisco IOS Dial
Technologies Command Reference. To locate documentation of other commands that appear in this
chapter, use the command reference master index or search online.
External Modems on Low-End Access Servers
Some of the Cisco lower-end access servers, such as the Cisco AS2511-RJ shown in Figure 23, have
cable connections to external modems. The asynchronous interfaces and lines are inside the access
server.
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Automatically Configuring an External Modem
Figure 23 Cisco AS2511-RJ Access Server
9 ASYNC 10 11 ASYNC 12 13 ASYNC 14 15 ASYNC 16
1 ASYNC 2 3 ASYNC 4 5 ASYNC 6 7 ASYNC 8
Modem
When you configure modems to function with your access server, you must provide initialization strings
and other settings on the modem to tell it how to function with the access server.
This section assumes that you have already physically attached the modem to the access server. If not,
refer to the user guide or installation and configuration guide for your access server for information
about attaching modems.
Configuring and Managing External Modems
Cisco AS2511-RJ
Modem
Modems are outside
the chassis
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Automatically Configuring an External Modem
The Cisco IOS software can issue initialization strings automatically, in a file called a modemcap, for
most types of modems externally attached to the access server. A modemcap is a series of parameter
settings that are sent to your modem to configure it to interact with the Cisco device in a specified way.
The Cisco IOS software defines modemcaps that have been found to properly initialize most modems so
that they function properly with Cisco routers and access servers. For Cisco IOS Release 12.2, these
modemcaps have the following names:
• default—Generic Hayes interface external modem
• codex_3260—Motorola Codex 3260 external
• usr_courier—U.S. Robotics Courier external
• usr_sportster—U.S. Robotics Sportster external
• hayes_optima—Hayes Optima external
• global_village—Global Village Teleport external
• viva—Viva (Rockwell ACF with MNP) external
• telebit_t3000—Telebit T3000 external
• nec_v34—NEC V.34 external
• nec_v110—NEC V.110 TA external
• nec_piafs—NEC PIAFS TA external
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The hayes_optima modemcap is not recommended for use; instead, use the default modemcap.
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Cisco IOS Dial Technologies Configuration Guide
Configuring and Managing External Modems
Enter these modemcap names with the modemcap entry command.
If your modem is not on this list and if you know what modem initialization string you need to use with
it, you can create your own modemcap; see the following procedure “Using the Modem Autoconfigure
Type Modemcap Feature.” To have the Cisco IOS software determine what type of modem you have, use
the modem autoconfigure discovery command to configure it, as described in the procedure “Using the
Modem Autoconfigure Discovery Feature.”
Using the Modem Autoconfigure Type Modemcap Feature
Step 1 Use the modemcap edit command to define your own modemcap entry.
The following example defines modemcap MODEMCAPNAME:
Router(config)# modemcap edit MODEMCAPNAME miscellaneous &FS0=1&D3
Step 2 Apply the modemcap to the modem lines as shown in the following example:
Router# terminal monitor
Router# debug confmodem
Modem Configuration Database debugging is on
Router# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)# line 33 34
Router(config-line)# modem autoconfigure type MODEMCAPNAME
Router(config-line)#
Jan 16 18:12:59.643: TTY34: detection speed (115200) response ---OK--Jan 16 18:12:59.643: TTY34: Modem command: --AT&FS0=1&D3-Jan 16 18:12:59.659: TTY33: detection speed (115200) response ---OK--Jan 16 18:12:59.659: TTY33: Modem command: --AT&FS0=1&D3-Jan 16 18:13:00.227: TTY34: Modem configuration succeeded
Jan 16 18:13:00.227: TTY34: Detected modem speed 115200
Jan 16 18:13:00.227: TTY34: Done with modem configuration
Jan 16 18:13:00.259: TTY33: Modem configuration succeeded
Jan 16 18:13:00.259: TTY33: Detected modem speed 115200
Jan 16 18:13:00.259: TTY33: Done with modem configuration
Automatically Configuring an External Modem
Using the Modem Autoconfigure Discovery Feature
If you prefer the modem software to use its autoconfigure mechanism to configure the modem, use the
modem autoconfigure discovery command.
The following example shows how to configure modem autoconfigure discovery mode:
Router# terminal monitor
Router# debug confmodem
Modem Configuration Database debugging is on
Router# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)# line 33 34
Router(config-line)# modem autoconfigure discovery
Jan 16 18:16:17.724: TTY33: detection speed (115200) response ---OK--Jan 16 18:16:17.724: TTY33: Modem type is default
Jan 16 18:16:17.724: TTY33: Modem command: --AT&F&C1&D2S0=1H0-Jan 16 18:16:17.728: TTY34: detection speed (115200) response ---OK--Jan 16 18:16:17.728: TTY34: Modem type is default
Jan 16 18:16:17.728: TTY34: Modem command: --AT&F&C1&D2S0=1H0-Jan 16 18:16:18.324: TTY33: Modem configuration succeeded
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Manually Configuring an External Modem
Jan 16 18:16:18.324: TTY33: Detected modem speed 115200
Jan 16 18:16:18.324: TTY33: Done with modem configuration
Jan 16 18:16:18.324: TTY34: Modem configuration succeeded
Jan 16 18:16:18.324: TTY34: Detected modem speed 115200
Jan 16 18:16:18.324: TTY34: Done with modem configuration
Manually Configuring an External Modem
If you cannot configure your modem automatically, you must configure it manually. This section
describes how to determine and issue the correct initialization string for your modem and how to
configure your modem with it.
Modem command sets vary widely. Although most modems use the Hayes command set (prefixing
commands with at), Hayes-compatible modems do not use identical at command sets.
Refer to the documentation that came with your modem to learn how to examine the current and stored
configuration of the modem that you are using. Generally, you enter at commands such as &v, i4, or *o
to view, inspect, or observe the settings.
Configuring and Managing External Modems
Timesaver You must first create a direct Telnet or connection session to the modem before you can send an
initialization string. You can use AT& F as a basic modem initialization string in most cases. To
establish a direct Telnet session to an external modem, determine the IP address of your LAN
(Ethernet) interface, and then enter a Telnet command to port 2000 + n on the access server, where n
is the line number to which the modem is connected. See the sections “Testing the Modem
Connection” and “Managing Telnet Sessions” for more information about making Telnet
connections.
A sample modem initialization string for a US Robotics Courier modem is as follows:
&b1&h1&r2&c1&d3&m4&k1s0=1
Modem initialization strings enable the following functions:
• Locks the speed of the modem to the speed of the serial port on the access server
• Sets hardware flow control (RTS/CTS or request to send/clear to send)
• Ensures correct data carrier detect (DCD) operation
• Ensures proper data terminal ready (DTR) interpretation
• Answers calls on the first ring
Note Make sure to turn off automatic baud rate detection because the modem speeds must be set to a fixed
value.
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The port speed must not change when a session is negotiated with a remote modem. If the speed of the
port on the access server is changed, you must establish a direct Telnet session to the modem and send
an at command so that the modem can learn the new speed.
Cisco IOS Dial Technologies Configuration Guide
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