Connecting via both Airport & Ethernet?

Question

I have a Mini (10.6.2) and a MBP (10.6.2) which are connected to a Airport Extreme for Internet connectivity. However, file transfers and screen share is slow (the Mini only has 802.11G, no N). So I was thinking I could connect these 2 machines via Ethernet only for file transfers and screen sharing.
Can these machines connect to each other via ethernet (to be used only for files sharing & screen sharing with each other) while being connected to the Internet via the Extreme? There must be some routing issues. Would this require some manual setup of the ethernet IPs (for example, using non-routable addresses like 172.16.0.1 & 172.16.0.2)? But then how to route everything to the Extreme (for Internet access) with the exception of 172.16.0.x for files and screen sharing?
Thanks in advance,
Charles

Answer 1

I think you are saying the Mini and MBP are close to each other. The simple answer is yes, you can do exactly what you want. Set static addresses for the wired network to be their own range (e.g. 192.168.1.x for the wireless and 192.168.2.x for the Ethernet (mask of 255.255.255.0 for both). The OSX networking should be smart enough to know which route is best for each situation - e.g. Internet will only work over the wireless, and the shortest route between the Mini and MBP is between each other over the Ethernet. You should be able to use a crossover cable between them and get the best speed that way.
If it gets confused, there are a number of ways around it. You can get into the routing tables, but that's the tricky way. You could set up the AE to specifically not allow the computers to see each other, and they will be forced to use the wire.
The simplest way to go with this setup is to use IP addresses when connecting to each other - then you're telling it which way to go. i.e. if you're trying to connect to 192.168.2.2 from 192.168.2.1, then the only way it can do it is to talk over that network. You could also manually set up a hosts file with a unique name/alias for each other (then use those names to talk to each other).
In my old Windows days, I'd get around all of this by setting the Internet link to use TCP/IP, and the link between PCs to use Netbui (and turn off Netbios on the TCP/IP link). You might be able to do something similar by using Appletalk on the wired link (not sure, as I don't know if you can still use that on 10.6.2).
If all else fails, use one as a gateway to the other. Turn off wireless completely on the Mini. Share your Internet connection on the MBP. That way all traffic from the Mini would have to pass through the MBP over the wire, so it would effectively be the only link between them, and all local traffic would be forced over Ethernet. The MBP would have to be on all the time though, or the Mini wouldn't get access to the Internet.
There's probably lots more ways to do it, but yes, you can do exactly what you are asking. It's all just packets being routed around.