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ATPM 8.11
November 2002

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Networks in Action

by Matthew Glidden, mglidden@atpm.com

Switching Between Networks in Mac OS X

Introduction

Mac OS X significantly changes the way your Mac deals with networks. After years of juggling multiple control panels, seemingly random collections of extensions, and network terms that read like alphabet soup, OS X has only “Network,” a single panel in the System Preferences. Whether you use Ethernet, AirPort, or whatever, it all funnels through Network.

My own network consists of an AirPort-enabled Mac Cube and the occasional Windows laptop (courtesy of my corporate masters). Ninety-nine per cent of the time, I connect to the Internet world through AirPort, a blissful existence free of wire and worries. Sometimes, however, I need to copy an essential document (i.e., “tiny_dancer.mp3”) from the laptop, which lacks a wireless card. Since the AirPort Base Station is in a different part of the building, the only option is connecting the laptop and Mac directly. Fortunately, the Mac easily falls back to its built-in Ethernet port, but it takes a bit of reconfiguring.

Step One: Hardware Hookup

Hooking up the laptop to the Mac is no problem, just connect both Ethernet ports using a crossover cable. Find a crossover cable in the network section of your favorite (or even second favorite) computer store.

ethernet_crossover

Two-Computer Crossover Connection

Step Two: Switch to Ethernet

Opening the Network panel on the Cube shows “AirPort” as the active connection. We need to change this to “Built-in Ethernet,” so choose “Active Network Ports” from the “Show” pop-up menu.

network-airport

Check the Ethernet port and either disable the AirPort port or drag Ethernet above it on the priority list. Choose “Apply Now” and the Ethernet port becomes active.

network-active

Switch the “Show” pop-up menu to “Built-in Ethernet,” then choose “Manually” from the “Configure” popup. Enter an address like 192.168.1.1 (the 192.168 prefix is reserved for private networks) and choose “Apply Now.” This gives the Mac an IP address, which you need to make the file transfer from the laptop.

network-manual

Step Three: Configure the Laptop

Configuring the Windows laptop (mine runs Windows 2000) is similar to the Mac. To assign an IP address, open the Network control panel from Start Button>Settings>Control Panels. Highlight the TCP/IP protocol connected to your network interface and click on “Properties.” Select the “IP Address” tab and enter the IP address (192.168.1.2, for example—just make it different from the Mac) and subnet mask (255.255.255.0). Close the Network control panel.

Step Four: File Transfer

Transferring files between computers requires a way for them to communicate, as AppleTalk allows Macs to talk to each other. Since AppleTalk isn’t a convenient option for my laptop, I use an FTP (file transfer protocol) server instead. FTP is just like it sounds, good for file transfer, but without much glitz and glamor.

I run the FTP server on my laptop, then use an FTP client on the Mac to upload and download files. For help setting up the FTP server and client, see Basic FTP File Sharing Between Macs and PCs from ATPM 7.11. For downloading files, most Web browsers will also work as FTP clients.

Downloading files is as easy as connecting to 192.168.1.2 from the Mac’s FTP client (or ftp://192.169.1.2/ from a browser). Once I’ve selected and transferred my (shockingly important) files from one to the other, I can disconnect the crossover cable and shut down the laptop, freeing my Mac to return to its natural, wireless state.

Step Five: Back to AirPort

Open the Network panel again (from System Preferences), then choose “Active Network Ports” from the “Show” pop-up menu. It’s time to re-enable AirPort and disable Ethernet, then choose “Apply Now.” Choose “AirPort” from the “Show” popup and “Using DHCP” from the “Configure” popup. Wait a few moments and you should receive a new IP address, indicating AirPort is up and flying again. Success! The switch is complete.

Technical note: I’ve noticed that AirPort won’t successfully reconnect until I unplug the Ethernet cable, even if I’ve disabled the Ethernet port. I’m not sure why, and your mileage may vary.

Conclusion

Mac OS X handles multiple networks with minimal fuss, even with the extra baggage of Windows. My own temporary switch is a good way to demonstrate moving from one to the other and you (yes, you) might find yourself in the same situation one day (unless, of course, you already have “Tiny Dancer”).

appleCopyright © 2002 Matthew Glidden, mglidden@atpm.com. Matthew Glidden is the webmaster of Threemacs.com, a guide to constructing and maintaining home and small-office Macintosh networks. He can also tango and juggle, not necessarily at the same time.

Also in This Series

Reader Comments (13)

anonymous · November 5, 2002 - 15:55 EST #1
The diagram in step one should not show two Macs being hooked together because, in that case, you would not need a crossover cable (I believe. I have not tried this myself). This might confuse some readers, or at least make them unaware of a handy feature on their Mac.
Michael Tsai (ATPM Staff) · November 5, 2002 - 16:32 EST #2
Whether you need a crossover cable depends on the Mac, but a crossover cable will always work whereas a normal patch cable won't work with older Macs.
Bob Morel · November 5, 2002 - 18:56 EST #3
Nice web site. I use OS X on a Lombard at work (hospital environment) and I often have to do network troubleshooting. Mac OS X is great. I have at least six different networks I need to plug into, and with a click I can be on with no problem.
Eelko · November 6, 2002 - 05:55 EST #4
For those that do not want to veture into installing and setting up an FTP server on the PC, remember that you can also use the Mac as an FTP server and make the PC log in to your Mac (System Preferences, Sharing, FTP). Or you could turn on Windows file sharing on your Mac (System Preferences, Sharing, Windows file sharing) and log on to the Mac from the PC as if your Mac is a PC. For this last option, you will also need to change your account settings. Turn on 'user can connect from Windows.

What is most important is that you don't forget to set your settings back to what they were, as you might otherwise have problems connecting to the internet and leave yourself vulnerable on the web.
Krioni · November 6, 2002 - 14:25 EST #5
Traditionally, you need a crossover cable to connect two Macs together directly. You use patch cables to connect a Mac to a wall port (corporate network) or your own hub/router. However, many recent Macs (at least starting with all the TiBooks, and possibly even the new iMacs) have the ability to detect what cable is connected and can actually reconfigure the ethernet port to work with either a crossover or patch cable as needed. I don't need a crossover cable to connect my TiBook to any other computer, but I DO need a crossover cable to connect my iBook to my old PowerMac 8500.
UMAR · April 27, 2005 - 11:06 EST #6
I have a Mac laptop OS X and a PC Win XP Pro. I want to connect both using a switch for both file sharing and Internet sharing. Please help me in simple words.
Stacy · April 27, 2005 - 22:03 EST #7
we just bought a used Blue G3 OSX and want to put it on the localtalk network with our older beige G3's and 7200's. The new machine doesn't have a serial port, just USB ports. What is the least expensive way to get this on our network?
Raajkumar · June 11, 2005 - 22:33 EST #8
I have a G4 Apple Note Book and i have a dell Inspiron series Laptop. I try this way in my both computers. It is working very well.
Robert Hosking · January 4, 2006 - 22:21 EST #9
I just connected my PC running XP to my G3 running OS9.1 with a crossover cable and I have successfully accessed the web on my Mac through my PC's wireless USB network adapter. I set the TCP-IP control panel on the mac to Ethernet and DHCP. Then I right clicked on the PC's local area connection and the wirless connection in the network places control panel and choose "bridge connections". Now the mac is accessing the web through the PC. Cool! I'm getting a free internet wi-fi connection on the PC and now I can surf the web on the G3 too. Funky man.
Larry Buys · February 2, 2006 - 14:27 EST #10
Any thoughts as to how to do this with a USB bridge cable? I have two iMacs (both runing OS X.3.9) that I'd like to network...However, one of them has a problem on the logic board and the ethernet doesn't work. I was thinking that a USB cable between the two would be a simple thing to do...Not so. Help?
ATPM Staff · February 2, 2006 - 15:38 EST #11
Larry - as best I can see from some Google searches, there's no built-in functionality to do it. There are, however, software and special USB cable kits you can buy to accomplish it. I found several but had never heard of the brands. IOGear, however, makes one. They aren't necessarily known for being the cheapest for hardware, but they're well-known and they make solid products.

http://www.iogear.com/main.php?loc=product&Item=GUN161
LordRich · October 29, 2006 - 09:24 EST #12
Larry - you might be better off using IP over firewire between the two iMacs, that's been supported natively since 10.3.
LORRAINE HAMILTON · April 6, 2007 - 17:59 EST #13
hi,first time on this website,it is fab,well i need some basic information,i bought my son a mac osx and the problem is that we are having extreme difficulty in getting broadband provider that is compatable for this computer,we have a british telecom line but use talktalk as our source of calls,i emailed talktalk and they informed me that it is not compatable with mac os x,i am stumped as what to do ,any help would be greatful.

thanks.

l.hamilton

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