Let's say we have a router with a WAN IP assigned by DHCP: 1.1.1.1/255.255.255.255
The ISP subnet for it's lan interface is 82.5.167.161/255.255.255.248
My firewall behind this router is on WAN IP: 82.5.167.162/255.255.255.248
I setup a one-to-one NAT for a web server on IP: 82.5.167.163
How when an external user access the web server on the IP mentioned, does the router know to send the traffic to the firewall?