TCP/IP over LocalTalk

“I’m using my PowerBook Duo 280c over Apple’s LocalTalk Bridge to get access to my ethernet network. What do I need to get TCP/IP to flow through that, too? Where can I get it?”

As long as the machine running LocalTalk Bridge is running Open Transport (OT) 1.1.2 or later, the bridge will pass TCP/IP packets through the AppleTalk network. You’ll probably have to hardwire the IP address to the 280c, as well as the bridge machine, and set up your firewall to receive TCP/IP through the ethernet.

Let me say this the proper way.

Given a network with two Quadra 610‘s and a Mac IIsi without an ethernet card, I can take advantage of TCP/IP fast network copies (I’m talking about Speed Doubler‘s option) on all machines by doing the following:

The Quadra 610’s are networked together with ethernet; one is set up to use LocalTalk Bridge for the IIsi. In OT, I setup the bridge as 10.0.0.1, and the other Q610 as 10.0.0.2. The IIsi is set up as 10.0.0.3, and the router address is 10.0.0.1 on all. DNS should probably point to 10.0.0.1 as well, even though you’re not really resolving anything on this ad hoc network.

Speed Doubler can copy through the LocalTalk bridge from the IIsi (10.0.0.3) to the Q610 without the bridge (10.0.0.2), through 10.0.0.1, without issue. LocalTalk copies run about 30% faster with Speed Doubler over TCP/IP.

This, of course, is all built into the current OT protocol. Given a machine that is only running MacTCP (part of Classic Mac Networking in System 7.5.5 and earlier), this still works. The main issue is that the bridge (10.0.0.1) must be running OT 1.1.2 or higher to adequately route TCP/IP packets through the LocalTalk Bridge.

Some of you may recall that LocalTalk Bridge wasn’t compatible with OT when it first came out, and this was because OT primarily speaks TCP/IP, which the original LocalTalk Bridge couldn’t handle properly. It used to require an Apple IP Gateway to handle the encapsulation, but with OT, Apple rolled that into the OS.

The important thing is to not try this with a MacTCP network – either you need one machine running OT 1.1.2 to handle all bridging/routing internally, or you’ll have to have a dedicated Apple IP Gateway machine.

Scott L. Barber <serker@earthling.net>
Pres/CEO, SERKER Worldwide, Inc.
Providing Hardware/Networking/Telecomm for 13 years

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