The modem command &Dn (where ’n’ is a number) generally sets the modemresponse to the data terminal ready (DTR) signal from the server’s serial port. Thedesired response is that the modem will hold a connection while DTR is enabled, anddrop the connection when DTR is released. This is the mechanism by which the serverhangs up on a connection under normal conditions.Consult your modem manual for its specific response scheme for the &Dn command.Two strategies are available for dealing with the modem’s response to DTR:v Recoveryv PreventionBefore you use one of these strategies, determine if your server’s modem is set upproperly to respond to DTR.With the remote terminal connected to serial port 1 and defined as the primary consoledevice, there are two tests you can perform:1. Will the modem drop the connection after the System initialization completemessage displays at the remote terminal?If yes, the modem is set up correctly.If no, try another &Dn setting for your server’s modem. See your modem manual forthis information. The &Dn command appears in three places each in three of thesample modem configuration files:v modem_f.cfgv modem_f0.cfgv modem_f1.cfg2. Will the server’s modem disconnect when the power drops? You can make thisobservation at the remote terminal by commanding your server to shutdown andpower off. (The AIX command shutdown -F will do this.) Watch for the message NOCARRIER on your remote terminal.If Yes, this is the correct response. The modem is set up correctly.If No, try another &Dn setting for your server’s modem. See your model manual forthis information. The &Dn command appears in three places each in three of thesample modem configuration.If you are using modem_z.cfg or modem_z0.cfg, you cannot control DTR response. Ifyour remote terminal does not disconnect after logging off, you must command theremote terminal emulator to hang up. This then breaks the connection.Recovery StrategyThe recovery strategy consists of making two calls to establish a remote session. Thisis the easiest solution to implement, and allows more freedom for configuring yourserver’s serial ports.298 Service Guide
