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ATPM 6.03
March 2000



How To



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How To Become a Network Guru in 10 Easy Steps

by Matthew Glidden,

Part 6—Frequently Asked Network Questions

Q: I want to use Apple’s (free) LocalTalk Bridge or LaserWriter Bridge, but it doesn’t work for me. Why not?

A: LocalTalk Bridge and LaserWriter Bridge are fairly old and haven’t been updated by Apple for some time. While version 2.1 of both programs is compatible with Open Transport, an article in the Apple Tech Info Library states that “Apple has done only limited testing with Apple LocalTalk Bridge under Mac OS 8.5. LocalTalk Bridge 2.1 is not completely compatible with Mac OS 8.5, and no update to this product is expected.”

This is primarily because of the large number of under-the-hood modifications to 8.5’s networking software, and thus there doesn’t seem to be a way around it. You may want to consider using a hardware Ethernet-to-LocalTalk adapter instead. Asante and Farallon both make such adapters.

For more information on LocalTalk Bridge and LaserWriter Bridge, see these links:

• • •

Q: To share access to a high-speed Internet connection, can I just connect my Macs to a hub and start using them right away?

A: How you connect more than one Mac to high-speed Internet depends on what kind of account you have. In order to just use a hub and attach all your Macs to it (see figure below), your Internet provider must allow you to get an IP address for each connected Mac. Most Internet providers let you use additional IP addresses for an extra fee of $10–15 per month.


If you only have a single IP address and want to share the incoming signal with more than one Mac, you need to use a hardware or software router to create “virtual” IP addresses for each Mac, since they’re all actually sharing the same address. Software routers are less expensive than hardware routers, but are also more complex to set up. For information on this kind of setup, see this section of the Web site.

If you use a software router to share your Internet connection, I suggest adding a second Ethernet port to the host Mac (see figure below), for security reasons. If you connect the incoming signal directly to a hub, your Internet Service Provider can “probe” the Internet connection and retrieve a list of all connected Ethernet devices. If you connect the incoming signal to a second Ethernet port, it will only see the second port, keeping your other Macs secure. Sharing the Internet connection may violate your service agreement, and the provider may choose to disconnect the service.


If you connect more than one Mac to a hub without additional IP addresses or a router, the first Mac that powers up will grab the available IP address. Any other Mac that powers up afterwards won’t be able to use the IP address, since it’s already taken.

• • •

Q: I tried to switch my Mac to “Ethernet” in the AppleTalk control panel, but it tells me to check my Ethernet connections and switches back! Why?

A: When you get this message, it means that your Mac tried to send signals through the Ethernet port, but didn’t get anything in return indicating there were other Ethernet devices. Typically, this happens when using a single “crossover” cable to connect two Macs without a hub. In order to make this kind of connection work, you usually need to switch both Macs over at the same time, so both Macs will send signals to each other. Unless the Macs are right next to each other, this probably means you’ll need help from a friend so you can get both Macs switched at the same time.

• • •

Q: What’s the cable length limit for Ethernet?

A: For twisted-pair Ethernet (the most common kind), the maximum cable length between hubs or computers is 100 meters. If you need to run a length of cable over that amount, you can purchase a “repeater,” which amplifies the signal and allows it to travel another 100 meters. Keeping cable lengths down is tricky, though. Generally, the best way is to calculate distances in advance, and determine the best place for the hub that is the closest possible point to all networked computers.

• • •

Q: I have a Power Mac (75/85/9500, et al.) that has built-in RJ-45 and AAUI Ethernet ports. Can I use both at the same time?

A: If your Mac has two built-in Ethernet ports, you can only use one or the other because both ports use the same internal Ethernet hardware. Note that having two ports built in to your Mac is different than adding a second Ethernet port via a PCI card or other expansion device. If you add a second Ethernet port via expansion, you can use both ports at the same time, although they must be for different networks (one for AppleTalk and one for TCP/IP, for example).

• • •

Q: I installed an Ethernet card in my Mac, but I can’t switch to Ethernet in the AppleTalk control panel or it’s not working like I think it should. What should I do?

A: When you install an Ethernet card in your Mac, it’s important to also install the correct software to go along with it. Your Mac needs the software so it can “see” the card correctly.

There are two kinds of Mac Ethernet cards: those that come built in to your Mac and those that are installed afterwards. Most beige-colored Power Macs have 10Base-T Ethernet built-in, and the more recent colored G3s, G4s, and iMacs have 10/100Base-T Ethernet built-in. If your Mac has built-in Ethernet, make sure that the “Ethernet Built-in” extension is in your Extensions folder. Owners of older Macs, like Quadras, with built-in Ethernet may need to use the “Apple Built-in Ethernet” extensions instead. This should let you switch to Ethernet in the AppleTalk control panel.

If you added Ethernet to your Mac with an expansion card, you need to install the software for the card so it will work correctly. Note that not all Ethernet card makers support the Mac, so you can’t always just pull an Ethernet card from another computer and have it work in your Mac. If the card you have didn’t come with software, check on the card maker’s Web site for the Ethernet software (which is usually called a “driver”). If the card supports the Mac, you should be able to get the software you need online. When you install the software, make sure you also disable other Ethernet extensions (such as the aforementioned “Ethernet built-in”), unless you’re using it for another Ethernet port.

• • •

Q: Is 100Base-T Ethernet actually ten times faster than 10Base-T?

A: Although 100Base-T is rated at ten times the speed of 10Base-T, that’s a theoretical maximum and is hard to even approach in real life. 100Base-T is typically more like three to five times faster than 10Base-T. The exact performance of a network will vary according to software, hardware, amount of traffic, traffic type, and other factors that seem to work primarily towards reducing the overall transmission speed.

Copyright © 2000 Matthew Glidden. Matthew Glidden is the webmaster of, a guide to constructing and maintaining home and small-office Macintosh networks. He can also tango and juggle, not necessarily at the same

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Reader Comments (10)

Moataz Mohammed · April 22, 2001 - 22:17 EST #1
I want to make a network between 2 PCs without a hub, and I want to know how I can make a plug for a CAT 5 patch cable.
Paddy Blake · November 4, 2001 - 15:20 EST #2
I have installed an AirPort network and use it to access the internet via cable modem. Works great, but I can't find out how to access a USB printer connected to one of our machines via the network. I'm running OS X.1 on all machines. Help would be most appreciated.
Jim Arnott · November 19, 2001 - 21:02 EST #3
I sure miss the old three Macs and a printer site... But it didn't address the 'new' technology. I need to network an old PowerCurve and an iMac. I would like to be able to share the iMac's USB devices (Imation Super Drive and an HP scanner) as well as an Epson printer. I have a USB card for the 'curve. I was planning to ethernet (10baseT) the two systems together, but USB is all new to me. Maybe I can use the USB hub. Can I get there from here? Thanks in advance.
Greg Tetrault (ATPM Staff) · November 26, 2001 - 17:36 EST #4
Paddy - I don't use OS X, but this doesn't sound any different from the situation where computers are on an Ethernet network but the printer is connected through a serial port. The options in this situation are to get some kind of hardware adapter or software bridge to put the printer on the network or to send the original file or the spooled print file to Mac connected to the printer and then tell that Mac to print it (using Timbuktu Pro or perhaps AppleScript). Maybe OS X networks have something better than those options.
Sandy Snyder · February 27, 2002 - 13:53 EST #5
I teach at a high school and have a AppleTalk network set up. I have 14 G3s on the network, however, only 10 students can login to the shared server folder at any given time. What am I missing?
Chris Lawson (ATPM Staff) · February 27, 2002 - 18:10 EST #6
File Sharing supports a maximum of 10 users per shared machine.
Sean W. Spencer · November 1, 2003 - 15:24 EST #7
I have a cable modem and I play a game called W3. When I make a game for people to join, they can't and say it's because of my router, but I don't have one. How do I disconnect it or do whatever I need to do?
Lee Bennett (ATPM Staff) · November 1, 2003 - 16:50 EST #8
Sean - check the firewall settings in the Sharing preference pane (I'm taking for granted you're using OS X). Make sure the firewall is either disabled or, if you want to keep it enabled, open the port numbers that are used by your game. Online communities that support your game should be able to help you determine what those port numbers are.
Bob MacBean · November 2, 2006 - 19:26 EST #9
hi - if i use an AAUI transceiver to connect to 10/100BASE-T ethernet port, do i need to use a hub or can i just run the ethernet line directly between the computers ? - thanks, bob
Lee Bennett (ATPM Staff) · November 2, 2006 - 21:04 EST #10
Bob - I think the circumstance would be the same as if you were using modern computers. You'd either need a hub (switch) or a crossover ethernet cable to connect them directly.

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