Telnet and my TP-Link Router

I've got one of these: -

TP-Link TD-W8970 300Mbps Wireless N Gigabit ADSL2+ Modem Router

and I was looking to tweak my Signal/Noise Ratio (SNR) as per this: -

Broadband SNR Margin Tweak

This requires me to telnet into the router: -

telnet 192.168.1.254

which prompts me for my admin credentials.

I entered the credentials that I'd normally use for the web admin UI: -

http://192.168.1.254

However, I kept getting: -

Login incorrect. Try again.

when I entered my password.

Thankfully, Google came to the rescue, as per usual, with this: -

Cannot connect with TELNET - wrong username/password?

<snip>

It is a bug verified by TP-LINK support indeed. Actually, the password cannot be longer than 15 characters. If it is longer than 15 characters, only the first 15 will be saved as the password. When you login via web brower, it will only identify the first 15 as well and you can login. However, telnet still accept the complete password, so that you cannot login via telnet. But if you just type in the first 15, you will be login via telnet as well.

</snip>

Guess what ?

I have a nice long complex password, that's obviously (!) longer than 15 characters.

Therefore, the web UI automatically truncates after character 15, but telnet doesn't know that :-)

Once I explicitly truncated the password to 15 characters, I was in like Flynn.