Cisco Systems DC-145 User Manual
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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-EndAccess Servers

Some of the Cisco lower-endaccess servers, such as the CiscoAS2511-RJshown inFigure 23, have cable connections to external modems. The asynchronous interfaces and lines are inside the access server.

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Configuring and Managing External Modems

Automatically Configuring an External Modem

Figure 23 Cisco AS2511-RJAccess Server

Cisco AS2511-RJ

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ASYNC

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ASYNC 12

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ASYNC 14

15 ASYNC

 

 

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Modem

Modems are outside the chassis

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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.

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—GenericHayes interface external modem

codex_3260—MotorolaCodex 3260 external

usr_courier—U.S.Robotics Courier external

usr_sportster—U.S.Robotics Sportster external

hayes_optima—HayesOptima external1

global_village—GlobalVillage Teleport external

viva—Viva(Rockwell ACF with MNP) external

telebit_t3000—TelebitT3000 external

nec_v34—NECV.34 external

nec_v110—NECV.110 TA external

nec_piafs—NECPIAFS TA external

1The hayes_optima modemcap is not recommended for use; instead, use the default modemcap.

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Automatically Configuring an External Modem

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 themodem 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 themodemcap 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

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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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-compatiblemodems do not use identicalat 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.

Timesaver You must first create a direct Telnet or connection session to the modem before you can send an initialization string. You can useAT&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, wheren 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.

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.

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