DHCP & Cable Modems, PC Emulation, and School Networking May 6th, 1999 Well, hello there! Thanks for joining us. Have a seat right over here and we'll get started. No sir, you can keep your shirt on... in fact, PLEASE keep it on. Anyway, now that we've gotten the formalities out of the way, let's get started. Right on the heels of the release of MacOS 8.6, I've gotten a ton of e-mail and seen quite a bit of usenet traffic surrounding the purported "fix" for DHCP and the RoadRunner Cable Modem Service. There had been some problems in the past that the RoadRunner staff had attributed to Apple's DHCP implementation, and we all were waiting anxiously to see if it was fixed in OS 8.6. The answer is YES, folks, it was fixed. Unfortunately, there are some misconceptions as to what the problem actually was and what was causing it. There is a Macintouch arti cle that goes into detail on the problem, so I'm just going to scratch the surface. The gist is this: The Mac receives it's IP address from a DHCP server by performing an operation that's known as "leasing." That server keeps track of which IP addresses have been issued. When a computer no longer needs it's IP address, it "releases" it's "lease" on the address by telling the server that it doesn't need it anymore. Then the server can put it back into the pool of unused addresses and issue it to the next computer that comes along. The problem was that MacOS 8.5.x was NOT sending the "release" command that RoadRunner's DHCP server was expecting. Therefore, when you shut down your Mac, RoadRunner thought you were still logged in using that IP address (I know, this is just skimming the issue). If you restarted your Mac, it would go to get another IP address and, since the server was convinced that you were still using your old one, it would issue you a new one. That's fine. The problem is that RoadRunner keeps track of how many IP addresses you're using and, if you're over your quota (of 1 for most people), it won't let you do anything on the Internet. The only ways around this problem were to either shut down your machine and wait 3 hours for RoadRunner to realize you weren't using the address, or to reset your cable modem and restart. That's not so bad, but it was annoying. Now, with OS8.6 and the help of the TCP/IP Options Control Panel in the new Open Tran sport Extras, we can tell the system "Don't retain DHCP Lease on shutdown." This will force it to release it's IP address properly each time you shutdown and/or restart your computer, and all is well. Trust me, I've been running OS 8.6 for a few weeks now and it works great. HOWEVER, there are OTHER problems with RoadRunner that may cause you to have to "re-login" as well. RoadRunner maintains a "login server" that ALSO tracks the status of your connection. If that server resets or crashes (which happens very often, folks), then it's going to think you haven't logged in and won't let you out on the Internet. If this happens, you're still going to need to re-login to use your connection. I hope this helps explain things. If anyone has questions, let me know! And now for answers to questions that I've already received! George writes, "I'm the lone Mac user in a technological conservative law firm-we were using WordPerfect 5.1 DOS up until a few weeks ago! However, the partners are willing to subsidize my efforts to integrate a PowerBook G3 series (300 mhz) under PC emulation. I need to be able to hook up to a standard (at least according to our computer guru) Novell network, and access a file server and several printers on the network, as well as run some PC-only software. My question is which PC emulation product is better (and possibly easier) for my intended purpose, Virtual PC or SoftWindows? From my research, it seems that Virtual PC has attempted to emulate a Pentium MMX processor (possibly at the price of performance), whereas SoftWindows uses a combination of proprietary and standard Windows drivers to maximize performance. Is this correct? Is there any solution which is more stable? Any assistance would be greatly appreciated." George -- This question of "Virtual PC or SoftWindows" is one that's very commonly debated. With that, I'll give you advice based on my own personal experiences. I've used both products with quite a few customers (as well as home) and I'd have to give the nod to Virtual PC. Performance isn't going to be THAT much different for what you're doing there, and I've found Virtual PC to be more reliable, stable, and predictable. It's also easier for a Windows-oriented tech. support-type person to troubleshoot. SoftWindows performs its magic by both emulating hardware and making significant changes to the software (Windows) to make it work properly. This makes it "different" from a normal version of Windows and can cause problems in some situations. Most of these, of course, have been worked out, but the opportunity for problems is there. Virtual PC, on the other hand, provides a "hardware abstraction layer." This means that its magic is (for the most part) performed in its hardware emulation. With that, you can install normal, PC-standard versions of Windows95, Windows98, WindowsNT, Linux, FreeBSD, you name it on top of Virtual PC and it will run. While you probably will install one operating system and just stick with it, this flexibility makes it much easier to support than SoftWindows, so that's my vote! Either way you go, you may wind up having some trouble printing to non-PostScript printers. So much so that you might want to consider getting a Postscript printer if you don't already have one in the office. Good luck! Elliott writes, "I am a teacher in a small high school with about 50 Macs of various models that are networked . We have numerous older programs that require the color depth be at 256 before they will run. They will not set the depth by themselves so we need to use the control panels/control strips to change them. We use At Ease for Workgroups to control access to the internet and what programs each student/teacher can access/use. We also use it to monitor students to make sure they are working on their assignments and are in appropriate places on the internet. When we got newer models of MAC's (5500's and G3's) with the capability of having monitors set to millions of colors however, students quickly learned that by setting the colors to millions, we were locked out of observing them since the At Ease program only allows you to observe computers using thousands of colors or less. We are looking for a way to lock out (eliminate/disable) the use of millions of colors while still having access to the control strip/control panel to toggle between thousands of colors to 256 for the programs that required that. We do not want to just go on 256 colors only." Elliott -- I think there's a solution out there for you. Unfortunately, I don't have At Ease for Workgroups running here so I can't test it, but there's a control strip module called "Switch Res" available. Switch Res allows you to specify which bit-depth and resolution combinations appear in its menu from the Control Strip (or menu bar, I believe). You can also have it set the resolution according to the application that's being launched and limit users' access to the Control Strip altogether. I've used this on my machines here and have had great success with it. It's also fantastic for those of us who have a Monitors Control Strip module that shows more options that we really have available. Sometimes clicking on the wrong one can cause a major headache, and Switch Res will allow you to "lock out" those resolutions that your hardware doesn't support. Update to Novell access: After my advice in l ast week's column about connecting to a Novell server, I received a barrage of e-mail informing me that I overlooked another solution. And, well, they were right. I neglected to mention the Netware Client made by ProSoft Engineering. This software will allow you to make your Mac "speak Novell" as opposed to my advice of making Novell "speak Mac." I've used this client quite a bit and, while it's great for newer versions of Novell, I still wouldn't recommend using it for version 3.x. I've had some very quirky problems with using newer clients on older versions of the server operating system, not the least of which is frequent AbEnds (Abnormal End = System Crash) on the server itself. I don't know what the client is doing that causes it, but the most stable solution for Novell 3.x has been to install Services for Macintosh as I mentioned l ast week. However, if you're using Novell 4.0 or later, I would recommend looking into the options that ProSoft's client offers. Keep those questions coming, and I'll keep posting the answers!   P.S. Have a Nice Day.