This is a pretty clear example of someone not even having a basic grasp of how a network functions, yet making a big inflammatory website about it anyway.
Yep. He plugs his ISP's modem into the LAN side of his network (the uplink port - usually a LAN-side port with built-in crossover intended for chaining switches), then has two DHCP servers running on the same segment. Oops.
He specifically says he connected it to the WAN port. On that router there is a block of four ports for the LAN, and then a short distance away the port for connection to the WAN.
There is no special LAN port for chaining switches, as all 4 for the LAN ports (and the WAN port) automatically sense if they need to be crossover ports or not.
I find it ironic he refers to grc.com for security advice. Birds of a feather...
Funny, I had that exact thought.
When the author starts by describing his local network as a /8 network, I instantly lowered my expectations for the rest of the article.
troll (noun) one who says or does inflammatory things for the purpose of entertainment or seeing a reaction