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It won't stay on Ethernet!

Preface

One of the most frustrating problems in setting up your network can be the AppleTalk control panel telling you that it can't switch to Ethernet because it's "not available." If this happens to you, try to resist the urge to whack the Mac's screen and yell "Not available? It's right there!" This problem typically occurs on Macs with built-in Ethernet, especially when using a crossover cable qm_icon picture. Essentially, whatever is hooked to the Ethernet port (if anything) doesn't look like an Ethernet network to the Mac. Since the Mac is unable to change and see things the way you do, you must understand how the Mac sees things to remedy the problem.

Setting up a crossover network?

It's often challenging to use a crossover cable on Macs that come with built-in Ethernet (like Power Macs and Quadras), because they were designed with an Ethernet hub qm_icon picture in mind. When these Macs start up, the Ethernet port looks for signals from other Ethernet devices. If the Mac doesn't see any, it won't start sending signals of its own. If you use a crossover cable to connect two of these Macs together, neither Mac will ever start sending signals. It's kind of a chicken-and-egg problem.

With the release of the iMac, Apple seems to have changed their built-in Ethernet design to more readily support crossover connections. Here's a quote from their iMac overview: "Ethernet crossover cables allow two Ethernet devices (two computers or a computer and printer, etc.) to connect directly without the use of an Ethernet hub. In the past, these cables have been not supported by Apple. However, iMac can often benefit from using a crossover cable." Basically, Apple is saying that the iMac will also send signals during the startup process, allowing the second computer to detect it as an Ethernet device. For more details, check out the Macs Only iMac Crossover Ethernet page.

Check the connections

Make sure you're attached to a network and the network adapters are functioning properly. Note that your Mac handles LocalTalk and Ethernet differently: you can switch to LocalTalk without a network actually present, but built-in Ethernet won't work unless a network is hooked to the Ethernet port. On Ethernet hubs, there is an activity indicator (usually a red or green light) on each port. When information is passing through that port, the light illuminates. If there isn't any activity on the port your Mac is hooked to, that indicates there's a problem somewhere in the connection or in the port. Try plugging your Mac into a different port; if the problem goes away, you've found a bad port. Also try a different piece of cable, for the same reason.

Check the cables

One of the most common causes of network problems is a cable gone bad. A bad cable is not just one that has internal wires showing or that got chewed on by the dog, though. Internally, most cables actually contain several wires; one bad wire can make the whole cable non-functional, or (even worse) partially functional. So how do you know if you have a bad cable? Typically, you can try swapping it with another, since the odds of getting two new-yet-bad cables is small. To be absolutely sure, you can have a computer tech check the internal connections.

Are you using the right cable?

When you're setting up a network, it's possible to end up with a different cable in the mix than you'd intended, with the end result that the network doesn't work. The most common example is in an Ethernet qm_icon picture network, since both a crossover cable qm_icon picture and a straight-through cable qm_icon picture look identical from the outside, but have different internal functions. If you didn't buy the cable in question yourself, the easiest way to verify what type you have is to compare it with cables at a computer store or check with a computer tech.

Still not working?

Problem still not solved? Questions linger? If so, please send mail and I'll do my best to help out. I try to answer all mail with 24 hours, although it can take longer if the answer requires some research.

Contents of Three Macs & a Printer are ©1996-1999 Matthew Glidden (except for the bits that aren't).

Questions or feedback? Feel free to send mail.

[This page was last updated on 3/7/99; 2:06:27 PM.]



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