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Mac OS X 10.0, 10.1: How to Set Up AppleTalk Multi-Homing

Mac OS X versions 10.0 to 10.1.5 provide AppleTalk multi-homing under specific conditions, described in this document.

Note: In Mac OS X 10.2 or later, you may only use AppleTalk on one network interface, or on one of several port configurations of the same network interface (if thus configured). If you try to enable AppleTalk on a second port, you will receive a message reminding you that this will disable it on the first port.
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What is multi-homing?

"Multi-homing" means that your computer can simultaneously appear on two or more networks or network segments. For example: A multi-homing computer could be connected to the Internet using two independent connections from an AirPort card and an Ethernet port.

Note: Most computer users do not require multi-homing, and this document does not explore the motivations for or benefits of multi-homing.

Multi-homing may be limited to particular services or protocols, and the ability of an operating system to multi-home may vary between services and protocols.

Requirements for AppleTalk multi-homing

For AppleTalk, Mac OS X may multi-home when these conditions are met:
    1. Each network interface (port) is connected to a separate network segment.
    2. Accessible networks may not have any overlapping network numbers.
    3. Each network interface must have an AppleTalk seed router on its network segment.

When these conditions are not met, the Network pane of System Preferences will still allow you to make AppleTalk active on multiple ports; but the AppleTalk service will not actually be available on all selected ports.

A common scenario for an AppleTalk multi-homing issue occurs when a portable computer, such as an iBook, is used with an Ethernet port at a desk but with an AirPort card while mobile. If both the Ethernet port and the AirPort Base Station connect to the same AppleTalk network, then AppleTalk may not work as expected. This may appear as behaviors described in these technical documents:

106608: "Mac OS X 10.1: AppleTalk Does Not Work After Being Enabled"
106613: "Mac OS X: 'No AppleTalk Printers Are Available' Message"

How to manage network interfaces (ports)

Warning: To prevent any potential data interruption or loss, be sure that you have completed any active AppleTalk transactions before following these steps.

When AppleTalk is active on two or more ports and the requirements for multi-homing are not met, you should turn off or "deactivate" AppleTalk on all but one port. Alternatively, you may deactivate ports you are not using. You may quickly switch between configurations in which different ports are active by using the Location feature of the Network pane of System Preferences.

Deactivating AppleTalk on all but one port

You may allow AppleTalk on only one port by following these steps:
    1. Choose System Preferences from the Apple menu.
    2. Click Network.
    3. Select the port from the Show pop-up menu that you wish to use AppleTalk.
    Note: Prior to Mac OS X 10.1, the Show pop-up menu is named "Configure."
    4. Click the AppleTalk tab.
    5. Be sure that the checkbox for "Make AppleTalk Active" is selected.
    6. Click Apply Now.
    7. Using the Show menu again, select each remaining port and ensure that the "Make AppleTalk Active" checkbox is not selected for that port.

Deactivating a port

You may deactivate all activity on a port by following these steps:
    1. Choose System Preferences from the Apple menu.
    2. Click Network.
    3. Choose Active Network Ports from the Show pop-up menu.
    Note: Prior to Mac OS X 10.1, the Show pop-up menu is named "Configure," and the Active Network Ports item is named "Advanced."
    4. Click to deselect the checkbox next to ports that you wish to deactivate.
    5. Choose the port you left active from the Show pop-up menu.
    6. Click the AppleTalk tab.
    7. Be sure that the "Make AppleTalk Active" checkbox is selected.
    8. Click Apply Now.

Using the Location menu

By default, Mac OS X has one location named Automatic, and all ports are active. The name Automatic is to remind you that Mac OS X has the capacity to automatically search all active network ports for your connection to the Internet. You can create different "locations" in which different ports are active. A "Mobile" location could make only your AirPort card active, and a "Desk" location could make only your Ethernet port active.

Follow these steps to make a new location:
    1. Choose New Location from the Location menu.
    2. Type a name for your new location, such as Mobile, then click OK. The name of your new location appears in the Location menu. Any changes you make to the Network pane now apply to this location. The previous location ("Automatic" by default) will remain as you left it.
    3. Using the steps described in the sections above, use the Show menu to select and set up the ports as appropriate for this location.
    4. When finished, click Apply Now.
    5. Repeat these steps to create a location for each port on which you use AppleTalk, as works for your environment.

Once you have created locations, you may quickly switch between them by changing the Location menu in the Network pane of System Preferences and then clicking Apply Now.
Last Modified: Feb 17, 2012

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