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Ask Dave
by Dave Hamilton

He from whom all Mac knowledge flows...

Advanced Networking Help & Missing Extensions
June 8th, 2001

Happy June, everyone! Today marks the eighth day of June, 2001, and I think we all know what THAT means.

In any event, today's column focuses on routing and port mapping using an Airport Base Station, sharing resources in a "mixed" Windows and Mac network, and what to do when your Mac tells you you're missing key Extensions from your system. If you have a question of your own, you can e-mail me, or ask in the comments below. Alternatively, the Ask Dave/Tech Support forums are there for everyone to take a stab answering your questions, so feel free to post it there, too! For now, read carefully and enjoy!

Tom Eberle writes, "I just finished setting up a small LAN at home. The network consists of two computers sharing a single static IP Internet connection through an Apple Airport Base Station. The Base Station gives out IP addresses to my computers via DHCP. Now the question: Is there a way to access my computers from the outside world with Timbuktu? I'm quite a novice to networking and would appreciate any help you could give me."

Tom, you're in luck. The Airport Base Station uses a protocol called Network Address Translation (NAT) to share one IP address with multiple computers. Because of this, any connections from the "outside" world will really only see your Base Station, and nothing past it. Being that Timbuktu is running on a computer behind your Base Station, we'll need to do some tweaking to make it so that computers outside of your network there can access it properly.

The first thing you should do is to manually assign an IP address to the computer(s) running Timbuktu. DHCP could potentially assign a different address each time, and that will confuse what we're about to do. Apple has set a range of address to NOT be assigned by DHCP, just in case you need to do something like this. That range defaults from to Set your TCP/IP control panel to one of those addresses in that range (lets use as an example), set your Subnet Mask to, and set both your Router and Name Server address fields to That should keep things from changing via DHCP.

Assuming you can still successfully connect to the Internet, let's move on. If you can't, check to make sure that you haven't changed the default IP range for the Airport Base Station, otherwise you'll need to adjust the "10.0.1.x" numbers above. Now you need to tell the Base Station to route Timbuktu packets. Go to your Airport Admin Utility, open up the proper Base Station, click on the Network tab, and then click on Port Mapping. Here you'll want to map port 407 (the default for Timbuktu) to your computer (which, assuming you used the example above, is at That should do it. You should now be able to connect to your Airport Base Station-routed computer via Timbuktu from the outside world (assuming, of course, that you have Timbuktu running and set up to answer incoming TCP/IP-based connections).

Since all copies of Timbuktu answer on port 407, only one computer can answer at a time. However, if you need both computers to be able to answer, Netopia has provided a script that will allow you to change the default port for your incoming connections. That's available via a link from their Timbuktu support FAQ. Also make sure you're running the latest version of Timbuktu, which address some issues with incoming connections.

Juan DelRio writes, "I'm using two Windows PCs and one G4 at home and would like to disable AppleTalk completely and only use TCP/IP on the Mac. I know I can share files and games in this way but can I share my printer? (it has a JetDirect card). Also, is it possible for the G4 to see my Windows PCs in the network browser, in the same manner as I see them using (Windows) Network Neighborhood?

Greetings, Juan. You, too, are in luck! To answer your first question, HP's JetDirect card should allow you to connect your printer to the same Ethernet hub that you're using for your other three computers. Once connected, you need to configure your printer (usually via either the JetDirect software or on the printer's front panel display) to have an IP address in the same Subnet as your computers. Once you've done that, it should respond to standard LPR-based queries, and both your Macs and Windows PCs should be able to print to it without using AppleTalk at all.

As far as the second question, you'll need to get your Mac to "talk" the same networking protocols as Windows. A product like Thursby Software's DAVE or MacSOHO will essentially give your Mac the ability to use "Client for Microsoft Networks" and, as such, you'll see your Windows PCs from your Mac.

Tammy Lange writes, "I have a Performa 5200CD, and I am having problems trying to do anything other than play two different versions of Solitaire! My computer keeps talking about missing TCP/IP in the Extensions Folder which I believe I should already have. If I am wrong, are there any Disks/Software/Etc... I can get that might walk me through fixing this problem? Or will I HAVE to take it to a Professional? I have been told taking it to someone would cost from $60-$100 to get it fixed and that is if that is all that is wrong with it. My computer was not abused, I think what happened was that I "accidentally" trashed a few things here and there and messed it up. What an expensive lesson!!! Can my computer be fixed without putting ME in the poorer house?

Well, Tammy, I hate to summarily recommend against having a professional look at your computer. Not only is that because I have been in the business of repairing computers, but I've also seen that "costly" repair save people thousands of dollars and hours of their own time down the road. The right consultant can *certainly* be a time and life-saver, assuming they know what they're doing.

That said, I think we might be able to help you out. It sounds as though you're missing some key Extensions for your system, specifically those relating to Open Transport, which is Apple's umbrella name for their entire suite of network-related drivers and software. You can get this back one of three ways. The first, and simplest, way would be to just install the latest version of Open Transport on your Mac. That should solve this problem, assuming something else strange isn't going on and that you're running Mac OS later than 8.6. If that doesn't work, you can take your Mac OS system software and just do a maintenance re-install (that is, install the Mac OS on top of your existing installation). This will, in theory, replace all missing Extensions and such while keeping all your existing preference files. If *that* doesn't work, then you'll have to do a "clean" re-install of your OS (in recent versions, this is available by clicking the "Options" button in the installer, in previous versions, you need to hold down the Option key and click Install in the Installer application). This will create a brand new System Folder, wiping the slate clean. While this option will almost definitely solve the problem, it will require you to reset all your preferences and, in certain instances, even re-install some of your applications as well. Good luck! And don't forget... if something goes completely amuck, there is likely to be a consultant nearby who would be happy to straighten things out for you and, if they're good, explain everything they're doing so you don't have to call them if you have the same problem again!

That's it for today, folks! Feel free to send your questions to me at [email protected], or ask in the comments below. I'll see you in a few weeks!

P.S. Have a Nice Day.

is President and CEO of The Mac Observer, Inc. He has worked in the computer industry as a consultant, trainer, network engineer, webmaster, and a programmer for most of the last 10 years. During that time he has worked on the Mac, all the various Windows flavors, Be, a few brands of Unix, and it is rumored he once saw an OS/2 machine in action. Before that he ran some of the earliest Bulletin Board systems, but most of the charges have since been dropped, and not even the FBI requests that he check in more than twice a year.

Ask Dave is here to answer all the Mac questions you have. Networking, system conflicts, hardware, you ask it, he can answer it. He is the person from whom all Mac knowledge flows....

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