If someone else can replicate this issue then I suspect it's a router bug and it will need to be fixed with the next firmware update. When I try to login via the TPLINK admin screen I briefly see the message "dyndns" instead of my selection.
Remember the last time you went to 18.104.22.168 to check up on pictures of your niece? Of course you don’t, because you typed into your web browser instead of 22.214.171.124.
DDNS allows me to control my download server, even when I’m not connected to my local area network.
Some of DD-WRT users are using this DDNS feature for Wake-on-LAN and other task which is mainly done by the router’s web interface.
A DNS server resolved your human-friendly request of into a machine-friendly address that sent you, probably in a hundredth of a second or less, to Facebook.
Wouldn’t it be great if you could set up the same trick for your home network? It’s easy to for big companies to set up domain names like because the address of their web server is static (once they have the IP address it doesn’t change). People with residential connections get a dynamically assigned IP address.