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Advanced Networking for Mactintosh Professionals


User Guide


Building Your Own Low Cost Ethernet

Like many people, I have more than one generation of Macintosh computers at home that are networked together to share files and a LaserWriter. When I decided to upgrade my Local Area Network from LocalTalk to Ethernet, I had a lot of practical questions that didn't seem to be answered in any one place.

I created this page to describe the practical details of building your own low cost Ethernet.


Is It Really Worth Upgrading?

I think so. Ethernet offers about 5-10 times the performance of LocalTalk. Ethernet interface hardware is also better designed to off-load your CPU. It is much easier to continue working while sharing files or printing via Ethernet.


Why 10Base-T

Ethernet can use several different types of physical wiring or "media" to satisfy different design requirements. By today however, 10Base-T Unshielded Twisted-Pair (UTP) Wiring is by far the best choice for most installations.

Some key advantages of 10Base-T Wiring:

  • 10Base-T interfaces are already included on many desktop Macs
  • Can add or remove devices without disrupting the network
  • Easiest to test and track down any cabling problems
  • Can be upgraded to full-duplex and 100 Megabits per second

With 10Base-T, each segment of network cable connects exactly two devices. To connect more than two devices, you must use a "Hub" or multi-port repeater.


Can I Get By Without A Hub If I Only Want To Connect Two Devices?

Perhaps. While this can be made to work in many cases, it is not officially supported or recommended. Normally each 10Base-T cable segment runs between an end node such as a host or printer and a hub. Hub ports are designed to be connected to end nodes using a straight-through cable. To connect two end nodes directly, or two hub ports, it is necessary to use a crossover cable so that each transmitter is connected to the corresponding receiver at the other end of the cable as shown below.

I normally carry a 10Base-T crossover cable with my Powerbook in case I want to setup an instant two node network with another host. Before you assume this is all you need however, it is important to realize that many 10Base-T end nodes assume they are connected to a hub.

Upon Startup, Macs with built-in Ethernet normally check to see if they have a valid Ethernet connection before starting AppleTalk on the Ethernet port. If your Mac is connected to a hub this works as expected. If your Mac is connected through a crossover cable to another Mac that is not powered on, your system may complain there is a problem with your Ethernet connection and automatically switch to using LocalTalk. Even if the remote machine is turned on, you may still encounter problems getting your Mac to recognize it has a valid Ethernet connection. [I've been told Macs with built-in Ethernet look for a valid carrier on the receive line. Some Network Interface Cards provide this, others don't.]

A small 10Base-T hub is no longer expensive and gives your network room to grow.


  1. Some hubs provide an optional "uplink" port that is pre-wired or can be switched to connect directly to another hub, called an MDI-X (Media Direct Interface-Crossover) port.
  2. If you do use a crossover cable, be sure to label it carefully so you don't confuse it with other 10Base-T cables.


How Do I Choose A Good Low Cost Hub?

I like the TRENDnet TE-900 series because:

  • An 8-port hub costs about $70.
  • The hub provides two diagnostic LEDs for each port to show the Link state (up or down), Rx data (blinking), and Partition (when a port has been isolated due to excessive collisions or other interface problem).
  • The designers didn't confuse the front panel with the rear panel. The front panel is clearly labeled and contains all the diagnostic LEDs. The rear panel contains all the network and power connections.
  • The hub is small, lightweight, and can be wall mounted or stacked with other equipment (and the color even matches).

10Base-T hubs are generally very reliable and guaranteed for years. Choose a hub that complies with IEEE 802.3 specifications for use on 10Base-T UTP cabling based on price and any features you find attractive. Some hubs include a ThinWire 10Base-2 uplink port that can be useful if you encounter older 10Base-2 equipment, or as a "backbone" port for connecting more than four hubs.

You may see so called "managed hubs" advertised for considerably more money. Managed hubs allow a network administrator to view the hub's operating status from a remote management console. For small networks, it's easier to "manage" a hub by simply looking at the status LEDs on the front panel. Managed hubs are intended for larger networks with lots of equipment to keep track of.


What Do I Need to Know to Install My Own Wiring?

If all the stations you want to network are in a single room, you can simply run 10Base-T patch cables between each station and your network hub. If your network spans several rooms or floors, you will probably want to install wall jacks (similar to but not the same as common telephone wiring). Each cable segment between an end node and hub must not exceed 100 meters. You can daisychain or "cascade" up to four hubs using 10Base-T.

10Base-T uses 8-pin RJ-45 modular style connectors available from many electronic supply stores and catalogs.

Eight-conductor data cable contains 4 pairs of wires. Each pair consists of a solid (or predominantly) colored wire and a white wire with a stripe of the same color. The pairs are twisted together. To maintain reliability, you must connect each pair to the appropriate pins and not untwist them any more than necessary.

Data cables normally use AWG #22-26 wire with #24 the most common. Solid conductor is preferred for longer runs and in-the-wall wiring, while more flexible stranded conductor cables are generally used for patch cords. If you decide to buy a crimping tool (about $40 for a decent one) and make your own cables, notice there are different RJ-45 plugs for solid versus stranded conductor cable. The more common modular plugs are designed for stranded patch cable. Look for specially labelled solid conductor plugs if that is what you need.

PVC insulation is fine for patch cords, but for in-the-wall wiring, you should use cable with a "Plenum" or Teflon jacket to meet fire safety codes.

Two grades of data cables and jacks are commonly available referred to as Catagory 3 (CAT-3) and Catagory 5 (CAT-5). The difference is that CAT-5 requires more twists per inch and can support 100 Megabit per second Ethernet. CAT-3 is usually a little less expensive and fine for 10 Mbps Ethernet. I always install CAT-5 for in-the-wall wiring since it is difficult to change later, but don't worry too much about patch cords.

The illustrations below give the correct wiring.

The pairs designated for 10Base-T Ethernet are Orange and Green. The other two pairs, Brown and Blue, can be used for a second Ethernet line or for phone connections. Note that the Blue pair is on the center pins and conveniently corresponds to the Red and Green pair in a normal phone line.

There are actually several different Color Code conventions for wiring RJ-45 plugs and jacks, so don't assume the wiring just by looking at the colors. As long as you follow a single convention that assigns wire pairs to the corresponding signals, you shouldn't have any trouble.


Do I Need A Transceiver?

Macs with built-in Ethernet may have one of two different interface connectors:

  1. An RJ-45 10Base-T port
  2. An AAUI (Apple Attachment Unit Interface) port

Some Macs include both. If your Mac already has a 10Base-T port (most PCI PowerMacs with built-in Ethernet), you don't need a separate transceiver. If your Mac only provides an AAUI port (NewBus PowerMacs and all 68K Macs with built-in Ethernet), you will need an AAUI to 10Base-T transceiver ($30-$40). The purpose of the AAUI port is that it allows you to select a transceiver for the type of Ethernet media you want to use (10Base-T, ThinWire, or ThickWire).

If your Mac doesn't include built-in Ethernet, you will need to get a Network Interface Card with the correct interface (10Base-T) for the media you want to use.


Now That I Have My Macs on Ethernet, How Do I Connect My LaserWriter?

You can choose one of your Macs to run Apple's "LaserWriter Bridge" software (free) to make any LaserWriters attached to that machine via LocalTalk appear on your AppleTalk Ethernet. The machine acting as the LaserWriter Bridge must be turned on for your other computers to print.

If you don't have an Apple LaserWriter or compatible printer, you can buy a software LocalTalk Bridge (around $50), or buy a dedicated hardware LocalTalk to Ethernet Bridge (around $250).


It's A Wrap

We hope you found this useful and welcome any comments.

Related Links

Macs + a Printer

Crossover Cables