05-Layer 2—WAN Access Configuration Guide

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06-Modem management configuration
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Managing a modem

About modem management

Modem is a widely used networking device. This chapter describes how to manage and control the  modems connected to the device.

Restrictions and guidelines: Modem management

Modem management is supported on the following user lines:

·     TTY lines for the following interfaces:

¡     Asynchronous serial interface.

¡     Asynchronous/synchronous serial interface operating in asynchronous mode.

¡     AM interface.

·     AUX line.

Modem management tasks at a glance

To manage a modem, perform the following tasks:

1.     Configuring modem services on a user line

Configure a user line for incoming modem calls, outgoing modem calls, or both.

2.     (Optional.) Setting the answer timeout timer

Increase the answer timeout timer on a slow link for a successful modem connection establishment.

3.     (Optional.) Setting the modem answer mode

You must set the modem answer mode on a user line to be the same as the connected modem.

4.     (Optional.) Enabling a modem to obtain caller numbers

This task is for point of sale (POS) terminal access services. Perform this task if a bank front end processor requires the call numbers of POS terminals for terminal identification.

5.     (Optional.) Enabling modem callback

Enable modem callback if the remote end connected to the modem requires a callback.

6.     (Optional.) Issuing an AT command to a modem

7.     (Optional.) Setting the country code of a modem

You must set the correct country code for the modem to operate correctly.

Configuring modem services on a user line

About this task

Perform this task on a user line to enable a modem to answer incoming calls, initiate outgoing calls, or both.

Restrictions and guidelines

This task disconnects the modem connection that has been established on the user line.

Procedure

1.     Enter system view.

system-view

2.     Enter user line view.

line { first-num1 [ last-num1 ] | { aux | tty } first-num2 [ last-num2 ] }

3.     Enable the modem to answer incoming calls, initiate outgoing calls, or both.

modem enable { both | call-in | call-out }

By default, a modem is disabled from answering incoming calls and initiating outgoing calls.

Setting the answer timeout timer

About this task

The answer timeout timer sets the amount of time that the modem will wait for a call to establish. When the timer expires, the modem disconnects the call.

·     If the modem is on the calling party side, the timer starts when the modem starts to dial.

·     If the modem is on the called party side, the timer starts when the modem goes off hook.

Procedure

1.     Enter system view.

system-view

2.     Enter user line view.

line { first-num1 [ last-num1 ] | { aux | tty } first-num2 [ last-num2 ] }

3.     Set the answer timeout timer.

modem answer-timer time

The default timer value is 60 seconds.

Setting the modem answer mode

About this task

To avoid modem answer failure, configure the modem answer mode on the device according to the current answer mode of the modem.

Set the modem answer mode based on the current answer mode of the modem:

·     Enable auto-answer mode if the modem is in auto-answer mode (the AA LED of the modem is on). This setting prevents the router from issuing an answer command after the modem answers a call.

·     Disable auto-answer mode if the modem is not in auto-answer mode.

Procedure

1.     Enter system view.

system-view

2.     Enter user line view.

line { first-num1 [ last-num1 ] | { aux | tty } first-num2 [ last-num2 ] }

3.     Set the modem answer mode.

¡     Enable auto-answer mode.

modem auto-answer

¡     Disable auto-answer mode.

undo modem auto-answer

By default, auto-answer mode is disabled.

Enabling a modem to obtain caller numbers

About this task

Perform this task if a bank front end processor requires the router to send the call numbers of point of sale (POS) terminals for acknowledgment before it accepts data from the terminals.

For more information about POS terminal access services and caller number sending, see Terminal Access Configuration Guide.

Restrictions and guidelines

This task is available only for POS terminal access services on the TTY lines of AM interfaces.

Performing this task disconnects the modem. Before you perform this task, make sure you are fully aware of its impact on the ongoing services.

Procedure

1.     Enter system view.

system-view

2.     Enter the TTY user line view of an AM interface.

line { first-num1 [ last-num1 ] | tty first-num2 [ last-num2 ] }

3.     Enable the modem to obtain caller number.

modem caller-number resolve [ ata-waiting-time time ]

By default, a modem does not obtain the caller number when it accepts a call from a terminal.

Enabling modem callback

About this task

The callback function enables a modem to disconnect an incoming call and calls back the calling party on request.

Procedure

1.     Enter system view.

system-view

2.     Enable the callback function.

modem callback

By default, the callback function is disabled.

Issuing an AT command to a modem

Restrictions and guidelines

This task changes the modem operating state. Incorrect configuration can cause problems such as dial-up failure. When you perform this task, make sure you understand its impact on the modem access service.

To send AT commands to a modem, you must first place the modem in AT command mode. To confirm that you can send AT commands, enter sendat at. The modem will return OK or 0 if it is ready to accept AT commands. For more information about commonly used AT commands, see Layer 3—WAN Configuration Guide.

Procedure

1.     Enter system view.

system-view

2.     Enter interface view.

interface interface-type interface-number

This command is available on the following interfaces:

¡     AM interface

¡     Asynchronous serial interface

¡     Asynchronous/synchronous serial interface in asynchronous mode

¡     AUX interface

3.     Issue an AT command to a modem.

sendat at-string

One sendat command can issue one AT command. To send multiple AT commands to a modem, repeat the sendat command.

Setting the country code of a modem

About this task

Modem encoding format differs with countries. You must configure the correct country code for a modem to function correctly.

Restrictions and guidelines

This task is available only on AM interfaces.

This task disconnects the modem connection.

Procedure

1.     Enter system view.

system-view

2.     Enter AM interface view.

interface analogmodem interface-number

3.     Set the country code.

country-code area-name

The default country code is united-states.

Modem management configuration examples

Example: Configuring modem management

Network configuration

As shown in Figure 1, configure DDR and modem access services for Router A and Router B to establish a modem dial-up connection between the Serial 2/1/0 interfaces for data transmission.

For more information about DDR, see "Configuring DDR."

Figure 1 Network diagram

 

Procedure

1.     Configure Router A:

# Create dialer access group 1 and add a dial access rule to match call triggering traffic. The rule in this example permits any IP packets to trigger a call.

<RouterA> system-view

[RouterA] dialer-group 1 rule ip permit

# Configure the asynchronous/synchronous serial interface Serial 2/1/0 to operate in asynchronous mode and protocol mode.

[RouterA] interface serial 2/1/0

[RouterA-Serial2/1/0] physical-mode async

[RouterA-Serial2/1/0] async-mode protocol

# Assign the IP address 1.1.1.1/16 to Serial 2/1/0.

[RouterA-Serial2/1/0] ip address 1.1.1.1 255.255.0.0

# Enable traditional DDR on Serial 2/1/0.

[RouterA-Serial2/1/0] dialer circular enable

# Assign Serial 2/1/0 to dialer access group 1.

[RouterA-Serial2/1/0] dialer-group 1

# Set the dial string for calling a remote end as 666666 on Serial 2/1/0.

[RouterA-Serial2/1/0] dialer number 666666

[RouterA-Serial2/1/0] quit

# Configure user line 1 (the user line for Serial 2/0) for both incoming and outgoing modem calls.

[RouterA] line tty 1

[RouterA-line-tty1] modem enable both

2.     Configure Router B:

# Create dialer access group 1 and add a dial access rule to match call triggering traffic. The rule in this example permits any IP packets to trigger a call.

<RouterB> system-view

[RouterB] dialer-group 1 rule ip permit

# Configure the asynchronous/synchronous serial interface Serial 2/1/0 to operate in asynchronous mode and protocol mode.

[RouterB] interface serial 2/1/0

[RouterB-Serial2/1/0] physical-mode async

[RouterB-Serial2/1/0] async-mode protocol

# Assign the IP address 2.2.2.2/16 to Serial 2/1/0.

[RouterB-Serial2/1/0] ip address 1.1.1.1 255.255.0.0

# Enable traditional DDR on Serial 2/1/0.

[RouterB-Serial2/1/0] dialer circular enable

# Assign Serial 2/1/0 to dialer access group 1.

[RouterB-Serial2/1/0] dialer-group 1

# Set the dial string to 888888 on Serial 2/1/0.

[RouterB-Serial2/1/0] dialer number 888888

[RouterB-Serial2/1/0] quit

# Configure user line 1 (the user line for Serial 2/0) for both incoming and outgoing modem calls.

[RouterB] line tty 1

[RouterB-line-tty1] modem enable both

Verifying the configuration

Verify that Router A and Router B can ping each other on their Serial 2/0 interfaces.

Troubleshooting modem faults

Symptom

An external modem is in an abnormal state. For example, the dial tone or busy tone keeps humming.

Solution

To resolve the issue:

1.     Execute the shutdown and undo shutdown commands on the physical interface connected to the modem.

2.     Power-cycle the modem.

3.     If the issue persists, contact H3C Support.

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