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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 imag
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9 ASYNC 10 11 ASYNC 12 13 ASYNC 14 15 ASYNC 16 1 ASYNC 2 3 ASYNC 4 5 ASYNC 6 7 ASYNC 8 Configuring and Managing External Modems Automatically Configuring an External Modem Figure 23 Cisco AS2511-RJ Access Server Cisco AS2511-RJ Modem Modems are outside the chassis 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 functi
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Configuring and Managing External Modems 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 the modem autoconfigure discovery command to confi
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Configuring and Managing External Modems 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
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Configuring and Managing External Modems Supporting Dial-In Modems Modems differ in the method that they use to lock the EIA/TIA-232 (serial) port speed. In the modem documentation, vendors use terms such as port-rate adjust, speed conversion, or buffered mode. Enabling error correction often puts the modem in the buffered mode. Refer to your modem documentation to learn how your modem locks speed (check the settings &b, \j, &q, \n, or s-register settings). RTS and CTS signals must be use
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Configuring and Managing External Modems Supporting Dial-In Modems Figure 24 EXEC Creation on a Line Configured for Modem Dial-In Idle state DTR low, watching CTS Ring transition Raise DTR Lower DTR Answer timeout DTR high, DTR low Hang up watching Ringing CTS Lower DTR close connection CTS raised Create EXEC CTS lowered or exit DTR high Ready and active Note The modem callin and modem cts-required line configuration commands are useful for SLIP operation. These commands ensure that when t
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Configuring and Managing External Modems Testing the Modem Connection Testing the Modem Connection To test the connection, send the modem the AT command to request its attention. The modem should respond with “OK.” For example: at OK If the modem does not reply to the at command, perform the following steps: Step 1 Enter the show users EXEC command and scan the display output. The output should not indicate that the line is in use. Also verify that the line is configured for modem inout
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Configuring and Managing External Modems Managing Telnet Sessions Step 4 The speeds of the modem and the access server are likely to be different. If so, switch off the modem, and then switch it back on. This action should change the speed of the modem to match the speed of the access server. Step 5 Check your cabling and the modem configuration (echo or result codes might be off). Enter the appropriate at modem command to view the modem configuration, or use the at&f command to return to
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Configuring and Managing External Modems Managing Telnet Sessions Suspending Telnet Sessions: When you are connected to an external modem, the direct Telnet session must be terminated before the line can accept incoming calls. If you do not terminate the session, it will be indicated in the output of the show users command and will return a modem state of ready if the line is still in use. If the line is no longer in use, the output of the show line value command will return a state of idl
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Configuring and Managing External Modems Modem Troubleshooting Tips Modem Troubleshooting Tips Table 14 contains troubleshooting tips on modem access and control. Table 14 Modem Troubleshooting Tips Problem Likely Cause Connection refused. Someone already has a connection to that port. or an EXEC is running on that port. or The modem failed to lower the carrier detect (CD) signal after a call disconnected, resulting in an EXEC that remained active after disconnect. To force the line back int
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Configuring and Managing External Modems Checking Other Modem Settings Checking Other Modem Settings This section defines other settings that might be needed or desirable, depending on your modem. Error correction can be negotiated between two modems to ensure a reliable data link. Error correction standards include Link Access Procedure for Modems (LAPM) and MNP4. V.42 error correction allows either LAPM or MNP4 error correction to be negotiated. Modems differ in the way they enable error
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Configuring and Managing External Modems Checking Other Modem Settings Cisco IOS Dial Technologies Configuration Guide DC-156
