Open the command prompt and run telnet.
Connect to <Router_LAN_IP> e.g. 192.168.1.1 so in the command prompt, this would look like:
When asked for the username, enter root (even if you changed username in web interface)
When asked for the password, enter your router’s password (default “admin”)
If for some reason you completely lost web access to the router, the web server (HTTP daemon) may be shut down. To regain access try starting the web server. SSH or telnet into the router and enter the following commands:
httpd -h /www