Reverse Telnet means that instead of initiating a telnet session from the Device/Terminal Server into the network, the session will be initiated from the network into one of serial ports on the Digi Device.

One popular benefit of this feature is the ability to eliminate multiple terminals that connect to various console ports by simply cabling each of the console ports to the Digi Device.

Before starting the reverse telnet set-up, verify that the correct IP Address Settings are configured and that you are running the latest firmware on the Digi Device.

Procedure:

There are two ways to configure the serial port for use with terminals.
A. Web Interface - see section on Configuring Ports for Reverse Telnet/Console Managment: Web Interface below.
B. Command Line - see section on Configuring Ports for Reverse Telnet/Console Managment: Command Line below.
NOTE: The PortServer or PortServer II units are not supported by the Web Interface and must be configured via the Command Line.  
NOTE: For more information and advanced features related to Reverse Telnet/Console Management see the product user/configuration manual.

Configuring Ports for Reverse Telnet/Console Managment: Web Interface

The Digi Device's serial ports must be configured properly before they will support console management.  To configure the serial ports for console management, do the following:
1.  From a web browser, enter the IP Address of the Digi Device and login root (default password is dbps). 
  

2.  Make the following changes from the Configure > Ports page. 
    A. For each port connected to a device that will be managed, change the device type to Printer.
        NOTE: The default device type setting for all ports is Terminal.
        

3. Make sure that the serial port and the device connected to the serial port are using the same flow control scheme and port parameters.
   NOTE: The default settings are: software flow control, 9600 bps, 8 bits, None for parity and 1 stop bit.

Configuring Ports for Reverse Telnet/Console Managment: Command Line

This procedure assumes the following:
A. That you are logged in as root
B. That you know the attributes, such as baud rate, parity, etc. required for use with the terminal that will be connected to this
     port.

1. Supply a set port command that specifies the following from the command prompt:
    #> set ports range=range dev=prn auto=off
    NOTE: where range is a port or range of ports.  This is the optimal setting for a reverse telnet as it puts the port into a "passive" mode, which
    will allow a session of data to go in "reverse."

2.  Supply a set line command that specifies the following from the command prompt:
    #> set line range=range baud=bps csize=characters parity=parity stopb=numbits
    NOTE: The set line configuration must match the settings of the attached terminal where:
    a.  range is a port or range of ports.
    b.  bps is the line speed.
    c.  characters is the character size.
    d.  parity is the parity scheme to use on this line.
    e.  num-bits is the number of stop bits to use.

3.  If your serial device is configured for hardware flow control, supply a set flow command that specifies the following from the
    command prompt:
    #> set flow range=range ixoff=off ixon=off cts=on rts=on
    NOTE: software flow control is the default, so a set flow command is not required in that case.
    NOTE: You may need to use additional set flow command fields, depending on the flow control scheme required by your
    serial device connected to the port.  See the set flow command in the Digi Device/Terminal Server Command Reference for more information.

Accessing Attached Devices by Using Telnet Direct to a Port (Reverse Telnet):

Testing a Reverse Telnet Connection:

Digi ships a loopback plug with its products.  This plug will look like a telephone jack, without any cable coming out of it.  Insert the loopback plug into the port you want to test.

Connect to the ports using one of the following standards:

2001 - 2099 Telnet Connect socket numbers.  An example is: telnet 192.1.2.3 2008 (for port 8 using ASCII data)

2101 - 2199 Raw Connect socket numbers.  An example is: telnet 192.1.2.3 2108 (for port 8 using RAW data)

When you get connected, you probably won’t see anything, although it's possible you would see a "Digi International PortServer" header along with the word "Connected."

With the loopback plug in the port, when you type some characters on your keyboard they should see them display on your screen.  This is an indication that everything is working correctly.  You should not be able to connect your device and reverse telnet/console manage it.  If you are not, you would want to verify the cabling from the Digi Device's serial port to the console port of your connecting device. Make sure that the cable you are using is a crossover cable.  Refer to the link below for appropriate cabling pin-outs.

http://supportold.digi.com/support/techsupport/hardware/portserver/common/cables/

Connect your cable, and make sure your devices "console" port is enabled for login. When you connect to the port again and press Enter, you should get a login prompt from the attached device, whether it be a Sun Sparc server, a Cisco router, or any other serial device.