User Manual

Security Dialback
11-6
11.3 Dialback
When dialback is used, the SCS verifies the identity of incoming users by logging the port out and dialing
the user back at a specified number. Dialback may be configured to do any combination of the following:
◆ Log out a port and call the user back
◆ Permit users to bypass the dialback process and connect immediately
◆ Terminate the connection when unauthorized users attempt to connect
Note: The port must be configured to use modems; for additional information, see
Chapter 9, Modems.
11.3.1 The Dialback Process
1 When a username is entered on a dialback port, the SCS determines if it should allow the connection
or dial the user back.
If the SCS must dial the user back, it hangs up the modem by cycling DTR.
2 The SCS sends a command to the applicable serial port. The command contains the modem command
prefix, the dial string, and the configured telephone number from its dialback database.
3 The dial string should perform any special configuration required for the call, then dial the remote
modem number (in the example below, 555-1235). It is not necessary to precede the telephone
number by strings such as "atdt."
4 The SCS waits the length of the Carrier Wait setting for the DCD signal to go high, indicating that the
modem has reconnected successfully. Otherwise, DTR is dropped for 3 seconds and the port is reset.
5 The SCS waits 30 seconds for the user to enter a username when in Dialback mode. After 30 seconds,
the port is logged out to keep unauthorized users from denying other users access to that port.
Note: Dialback only applies to incoming port logins. Dialback ports can be used
normally for outgoing connections.
11.3.2 Dialback from Character Mode
To use dialback for character logins, configure a list of authorized users with the following steps:
1 Enable modem control using the Define Ports Modem Control Enabled command.
2 Assign a modem type to the port using the Define Ports Modem Type command.
3 Enable dialback using the Define Ports Dialback Enabled command.
4 Configure how Dialback treats users who are not in the dialback database.
The Dialback Bypass setting controls what happens when a user that is not in the dialback database
attempts to connect to the SCS. If Bypass is enabled, these users will be allowed to connect without
dialback occurring. If Bypass is disabled, these users will not be able to connect.