Normal port vs Uplink port

http://networkengineering.stackexchange.com/a/23000

 

This has to do with how (UTP) Ethernet cabling works. In the old days, end point devices (like your PC) would use wires 1 and 2 to transmit data, and wires 3 and 6 to listen (https://en.wikipedia.org/wiki/File:Ethernet_MDI_crossover.svg) (*). The switch on the other side of the cable would listen on wires 1 and 2, and transmit on 3 and 6. Now if you would connect two siwtches, this would not work with a regular cable, because both switches would use the same wires in the cable to transmit. On solution for this is to use a special crossover cable, within which the cabling is crossed. Another solution is to have a specific "Uplink" port on the switch, which is wired as an end-point and uses the same wires to listen/transmit as a regular PC for instance.

With modern devices this is all a moot point, since practically every device uses "Auto-MDI-X" (https://en.wikipedia.org/wiki/Medium-dependent_interface#Auto_MDI-X) to sense which wire to listen and to transmit on. This standard was introduced in 1998, so it's very rare to find use for your old crossover cables today.

As for your Linksys switch: you can use the Uplink port to connect an end-point if you would use a crossover cable. However, in the internal wiring in the switch the Uplink port is the same port as port number 5 (http://www.linksys.com/id/support-article?articleNum=132646), so you can only use one of them (either the Uplink port, or port 5, not both simultaneously).

(*) This is true for 10BASE-T (10 Mbit/s) and 100BASE-TX (100 Mbit/s) Ethernet. Gigabit Ethernet uses all 8 wires in the cable.