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How to increase security in the D6686 or D6100IPv6 and how to return to factory default settings.


The D6686 or D6100IPv6 may be vulnerable to becoming inoperative if a telnet session is left open by any means not intended by its owner. Enabling a password for Telnet sessions will prevent an internet attacker from attempting to utilize the second available tunnel. 

  • Prerequisites: The PC used to make configuration changes must reside on the same subnet as the D6686 or D6100IPv6.

How to add a password to protect the telnet session:

  • This article applies to both the D6100IPv6 and D6686. Substitute D6100IPv6 in place of D6686 in all below examples when working with a D6100IPv6 .

  • Prompt display: When Telnet authentication is disabled the unit short name (default: D6686) will display, if a  short name has not been programmed, the symbol [ > ] will display.

  • If

    ‘login’:

    displays, this indicates the Telnet password has been enabled and will be required to access telnet.

  1. Open a command prompt and enter [telnet xxx.xxx.xxx.xxx] (where xxx.xxx.xxx.xxx is IP Address of the device) and press Enter.

  2. D6686> displays, type [en] and press Enter.

  3. D6686(enable)# displays, type [conf] and press Enter.

  4. D6686(config)# displays, type [cli] and press Enter.

  5. D6686(config-cli)# displays, type [login password] followed by [your new telnet password] and press Enter. Note: the password entered in step 5 will be required for all future telnet sessions in the D6686.

  6. D6686(config-cli)# displays, type [telnet] and press Enter.

  7. D6686(config-cli-telnet)# displays, type [authentication enable] and press Enter.

  8. D6686(config-cli-telnet)# displays, type [write] and press Enter to save the above changes.

  9. D6686(config-cli-telnet)# displays, type [ex] and press Enter.

  10. D6686(config-cli)# displays, type [ex] and press Enter.

  11. D6686(config)# displays, type [ex] and press Enter.

  12. D6686(enable)# displays, type [reload] and press Enter.

  13. Are you sure (yes/no)? displays, type the word [yes] and press Enter and the D6686 will reboot.  The next time the Telnet command is entered as in step 6, a login prompt will appear and the newly added Telnet password will be required.

How to remove the password from the telnet session:

  1. Open a command prompt and enter [telnet xxx.xxx.xxx.xxx] (Where xxx.xxx.xxx.xxx is IP Address of the device) and press Enter.

  2. D6686 login: displays, enter the default user name [admin].

  3. Password: displays, enter the Telnet password and press Enter.

  4. D6686> displays, enter [en] and press Enter.

  5. D6686(enable)# displays, enter [conf] and press Enter.

  6. D6686(config)# displays, enter [cli] and press Enter.

  7. D6686(config-cli)# displays, enter [telnet] and press Enter.

  8. D6686(config-cli-telnet)# displays, enter [authentication disable] and press Enter.

  9. D6686(config-cli-telnet)# displays, enter [write] and press Enter to save the above changes.

  10. D6686(config-cli-telnet)# displays, type [ex] and press Enter.

  11. D6686(config-cli)# displays, type [ex] and press Enter.

  12. D6686(config)# displays, type [ex] and press Enter.

  13. D6686(enable)# displays, type [reload] and press Enter.

  14. Are you sure (yes/no)? displays, type the word [yes] and press Enter and the D6686 will reboot.  The next time the Telnet command is entered as in step 1 the login will no longer display and the unit short name (default: D6686) displays.

How to return the D6686 to factory settings.

  1. Open a command prompt and enter [telnet xxx.xxx.xxx.xxx] (Where xxx.xxx.xxx.xxx is IP Address of the device) and press Enter. If the display reads: D6686 login:, enter the default user name [admin]. Password: displays, enter the Telnet password and press Enter.

  2. D6686> displays, type [en] and press Enter.

  3. D6686(enable)# displays, type [reload factory defaults] and press enter.

  4. A warning displays indicating all configurable parameters will be destroyed and that the unit will reboot.

  5. At the Are you sure you want to do this (yes/no)? prompt, type the word [yes] and press enter.

  6. Do you want to back out (yes/no)?  type the word [no] and press enter.

  7. Changes will take effect on next reboot.

    1. Rebooting ...

    2. After the reboot cycle finishes, the unit will now again be at the factory default settings.