CAT5 Crossover Cable:

Here's some guidelines for connecting one machine to another machine using Ethernet, with no other machines on the network. In this case, you don't need a hub; you just need to connect the wires between the two machines correctly. Refer to my page on color codes for detailed instructions on plugs and jacks.

To connect two machines to each other without a hub, you need a "cross-over" patch cable, which crosses the transmit and receive pairs, the orange and green pairs in normal wiring.

  One End     Cable  The Other End
TR+   pin 1 -------- pin 3 RCV+
TR-   pin 2 -------- pin 6 RCV-
RCV+  pin 3 -------- pin 1 TR+
RCV-  pin 6 -------- pin 2 TR-

Alternatively, you can connect two wall jacks back-to-back, swapping the orange and green pairs, to make a "two-port hub". Then you can use straight-through patch cords between each of the machine and one of the "hub" jacks. This is used to connect two 10baseT transceivers directly together, as in connecting the transceiver on your Mac to a transceiver on another Mac. I suppose you could connect a Mac to a PC, but why would anyone want to?. :-)

One more excellent suggestion was contributed by isw@hdvs.com (Isaac Wingfield). Make the crossover cable using a very short cable with a standard RJ-45 plug pinout on one end and a wall jack, cross-wired, on the other end. Then you use a single standard straight-through patch cord. Using this small cross-over "extension cord" prevents having two kinds of patch cords around and makes it very obvious what it is.