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Problem: Unable to Proxy through NetGuardian to Another Device

Platform: NetGuardian

Establishing a proxy connection to a device through the NetGuardian allows you to quickly access that device from a remote location. Setting up a proxy connection involves just a few quick steps. Use the following "techno knowledge" paper to troubleshoot common connection issues.

This "techno knowledge" paper can help you if:

  • You are unable to proxy to another device through a NetGuardian
Quick Reference Chart
flow chart
(For more details, review the Troubleshooting Checklist below)

Troubleshooting Checklist

  • Telnet to the correct port
  • The factory default is data port 1 on TCP port 3000, but this setting is customizable. Data ports 2 through 8 will follow consecutively after the first port (ex. 3001, 3002, 3003).
port 3000
To view or change your current port configuration, locate "Proxy Base" field on the "Ports" tab of your NetGuardian configuration software. NOTE: You must write the configuration file from your PC to the NetGuardian before any changes will take effect.
If you are attempting to Telnet to the correct port and still have a problem, proceed to the next step:

  • Telnet to the NetGuardian configuration screen and navigate to the desired port.
  • Two common Telnet clients that may be used are:
  • Windows Command Prompt, and
  • HyperTerminal

Windows Command Prompt

windows command prompt
In the Command Prompt window, type "Telnet", the NetGuardian's IP address, and "2002". Press Enter. password
If the connection is successful, you will be prompted for a password (default password is "dpstelecom").


Create a new connection by entering the NetGuardian's IP address and port number 2002. hyperterminal password
If the connection succeeds, enter a password (default password is "dpstelecom") to log on. telnet fail
If the connection attempt fails, please review "Unable to Telnet to NetGuardian - Techno Knowledge Paper" for further assistance data port
After entering your password, press 'P' to see a list of available ports.
Select the desired port from the list.
If the port is not listed, another device is using the port.
If this proxy connection fails, skip ahead to "Check the baud rate and format".
If this proxy connection is successful, proceed to the next step:

  • Set the port's type to TCP, HTCP, or RTCP.
prot type
On the "Ports" tab of your NetGuardian configuration software, set the port's type to the appropriate setting.
If you are still unable to proxy to your other device through the NetGuardian, check for firewall issues.

  • Match the NetGuardian baud rate and format to the external device
  • Check the baud rate on the port
  • Check the format (data/parity/stop bit)
Locate these lights on the front of the NetGuardian debug filter
If you are not at the NetGuardian's location, open a second Telnet connection and press 'D' led data
Press 'l' (lowercase) to see the current status of the front panel LEDs. ('-' is off, 'G' is green, 'R' is red)

led 2
Proxy to the desired port and press a key. The corresponding light should flash green.
If a different light turns green, check the NetGuardian database for a configuration issue.
If the correct light flashes green, short pin 2 to pin 3 on the data port connector and repeat the test.
led 3
Repeat the test by pressing a key. The light should flash green, then red. On your PC, you should see an echo of the keys that you type.
If you still cannot proxy to an external device through the NetGuardian, proceed to the next step:

  • Verify the cabling between the NetGuardian and the external device
  • Verify the port of the external device
  • Was the external device configured with a laptop before it was connected to the NetGuardian? If so, reconnect to the device with a laptop.
  • If the connection fails, the external device may have a bad serial port.
  • If the connection is successful, check the baud rate and data format of your laptop and configure the NetGuardian with the same settings.
  • Verify the pin-out of the device
  • When connecting to the device with a cable, was the cable straightthrough or modified?
  • If it was straight-through, you must null the cable between the NetGuardian and the device.
  • If it was modified, you will need to find or create a pin-out of the cable. A pin-out can be created with an ohmmeter.
  • If the device is a DTE device:
  • Connect the transmit pin of the NetGuardian to the receive pin of the device
  • Connect the receive pin of the NetGuardian to the transmit pin of the device
  • Connect the two ground pins together

  • Use a blinker box to check the state of the pins on your PC and the NetGuardian
  • The PC's RS-232 port pins should have the same state as those on the NetGuardian.
blinker box
Use a blinker box to test pin states.

  • Determine whether the device requires handshaking
  • You may be able to work around many problems by, for example, looping RTS to CTS and DTR to DCD on the device.

If you remain unable to proxy to an external device through the NetGuardian, please contact DPS Telecom Tech Support.