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Example: Configuring Modem Connections (NSM Procedure)


The modem is only available for some security devices. Use the Modem option to configure the security device for operation with an external modem. You can connect an external modem to the RS-232 serial port on certain security devices to enable the device to establish a PPP connection to an ISP. This provides a backup serial interface for traffic to the Untrust zone if there is a failure on the connection through the primary interface.

You can configure the parameters for the serial link as described in Table 1.


Range Value

Speed (BPS)

The maximum baud rate for the serial link (the default rate is 115,200 bps).


The maximum amount of time that the serial link can be idle before ScreenOS automatically disconnects the modem (the default is 10 minutes).

Retry Number

The number of times ScreenOS retries the dial-up connection if the line is busy or there is no response (the default is 3 times).

Retry Interval

The interval, in seconds, between dial-up retries (the default is 10 seconds).