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Open System Command:
http://192.168.1.1/Main_AdmStatus_Content.asp

Enter:
/usr/sbin/utelnetd -d
and click Refresh button.
You should now be able to Telnet to the router without any user/password so PLEASE check firewall rules and make sure Telnet access is blocked from WAN.
Anybody in LAN will be able to Telnet as root so beware.

To stop telnet daemon type ps to check PID ID and then kill it with
kill -9 xxxx
where xxxx is PID of utelnetd as seen with ps command
%%