What is the difference between a Home Router's WAN and Uplink port

Question

My old Planet XRT-401C router has these ports. My former ISP gave me a cable modem where I have to plug the lan cable from the cable modem to the WAN port. But now I'm switching ISP who provides me with a direct Ethernet cable into my home without a cable modem. By some trial and error I notice that now I need to plug the ISP's Ethernet cable to the Uplink port next to the WAN port.

But what is the technical difference between the 2? Also what is the 5th port labeled Uplink next the port labeled 1 and the what's the meaning of the line connecting the 2? The manual didn't explain any of these!

Answer 1

Assuming the ports are 100MBit/s, there is an easy explanation:

Back in the early days of 100Mbit/s, the ports on a switch and the ports on a NIC were different: Pair 1-2 on a switch connected to Pair 3-6 on a NIC and vice versa, in fact connecting the sending end of the Switch with the receiving end of the NIC and v.v.. To connect a switch to a switch or a NIC to a NIC, a special "crossover" cable had to be used - and since these cables were not always readily available when needed, vendors started to put "uplink" ports on their switches, routers, etc. that would carry the same signal, but in the crossover configuration, allowing for the use of a standard "straight" cable.

I assume your router has one of these pairs for Port 1 and one pair for the WAN side.

Your old router is not, but today all modern gear is auto-sensing, i.e. the correct configuration will be handshaked between the two sides, so it shouldn't matter.

For the LAN side chose the uplink port instead of port 1 if you want to connect to a switch.

For the WAN side, you already found out. Alternatively you could use a crossover cable and plug into the WAN (not uplink) port.