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What is the problem? The problem that prompted me to examine this for solutions is described by Apple on their web site as of the time of this writing for the Mac OS X Net-Booting servers.

  1. Only one Mac OS X Net-Booting Server may exist on a subnet at a time.
  2. The sample G3 server you can buy from apple (referenced on their web site) running Mac OS X with 4 ethernet interface for this kind of purpose) is capable of servicing 24 Net Booting Macintoshes.

Though net-booting a Macintosh that does client sided computing is a very good idea, and even better since many popular mainstream titles are supported as opposed to system like NCD's NC, and the Sun Microsystems Sun Ray. It *could* be more scalable if you could have a centralized DHCP Server hand out information for hundreds of machines on a single subnet to connect to multiple different netBooting Mac OS X server that have had their BootP disabled, or if their Mac OS X NetBooting BootP server had the ability to ignore requests from clients other than the ones specified by the Mac OS X Server's System Administrator.

Too bad that only one machine is allowed per subnet...

Why is it that only one machine is used per subnet? A brief review of the technical information on Apple's Website suggests a reason.

  1. The Server will give out Net-Booting information to any Net-Booting Macintosh that requests it. (Allowance to offer net booting service to any unknown client that asks for it.)
  2. BootP, TFTP, and AFPFS/IP are the protocols that are referenced. Of these, BootP is the only one that is limited by a Subnet. A BootP request is usually limited to one subnet, and stopped at routers.

I can tell you now, that it appears that the BootP issue appears to be the only problem limiting the inclusion of multiple NetBooting servers onthe same subnet!

    Some solutions that might work?
  1. If it were possible to tell the Server "I only want to you to serve to machines with these Hardware Addresses." then there would be no problem. you could populate many clients on the same subnet, and not need to worry about a random server talking to your clients.

  2. If it were possible to have the bootp information sent from a centralized campus DHCP server, then that would solve the problem, since you can turn off the BootP service on the NetBoot Manager while leaving the rest of the boot manager (TFTP, and AFPFS/IP) running.
  3. Another solution includes buying lots of Layer 3 switches and having servers located in labs, and then enabling blocking of bootp requests from leaving local lab networks, or coming into the local lab networks.
  4. Another solution includes using 2 or more ethernet interfaces on the server, and putting one ethernet interface on the campus network in the lab, and the rest of the ethernet interfaces onto a switch or hub that only serves the lab and only turning on NetBoot on the interface(s) that serve the lab, but this will run contrary to the Network administration of most campuses, since it places a router (since the Mac OS X server would be acting as one) in a lab setting, and is yet another networking device to maintain. (Presently Mac OS X does not do NAT or IP Masquerading with the software provided in the server.) This is one of the solutions suggested by Apple on their site.
  5. Another solution is to create a separate subnet for each lab by locating a router for each lab and locate the Mac OS X Server in this lab on that subnet, but this is a gross use of IP addresses: 1 for Network ID (bits off) 1 for broadcast (bits on), anther for an interface that is "wasted" on the router interface to the campus network.This is one of the solutions suggested by Apple on their site.
  6. Do you have other suggestions for ways to deal with this? Drop me a line to add the idea. Let me know if it is OK to include your e-mail address and name on the site to give you credit.

    [Designed for use with LYNX!]

    [Simple Network Analysis for Mac OS X Net Boot Server]
    [ DHCP v 2.0 ]

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