4000 Router Series Layer 2 - WAN Configuration Guide

# Configure the asynchronous interface Serial 2/0 to operate in protocol mode.

[Router] interface serial 2/0

[Router-Serial2/0] physical-mode async

[Router-Serial2/0] async-mode protocol

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

[Router-Serial2/0] ip address 1.1.1.1 255.255.0.0

# Enable C-DDR on Serial 2/0.

[Router-Serial2/0] dialer circular enable

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

[Router-Serial2/0] dialer-group 1

# Set the auto-dial interval of DDR to 5 seconds on Serial 2/0.

[Router-Serial2/0] dialer timer autodial 5

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

[Router-Serial2/0] dialer number 666666

[Router-Serial2/0] quit

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

[Router] line tty 1

[Router-line-tty1] modem enable both

To display user line information for an interface, use the display user-interface command.

2. Configure the Cisco Router:

For information about DDR dialup, see Cisco documentation.

Troubleshooting modem faults

Symptom

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. If the problem persists, power-cycle the modem.