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Ingmar Hupp
Asked: 2011-11-15 08:00:14 +0800 CST

How to configure TFTPD32 to ignore non PXE DHCP requests?

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I want to give our Windows guy a way of easily PXE booting machines for deployment by plugging his laptop into one of our site networks. I've set up a TFTPD32 configuration which does just that, and our normal DHCP server ignores the PXE DHCP requests due to them having some magic flag, so this part works as desired. However I'm not sure how to configure TFTPD32 to only respond to PXE DHCP requests (the ones with the magic flag) and ignore all normal DHCP requests (so that the production machines don't get a non-routed address from the PXE server).

How do I configure TFTPD32 to ignore these non-PXE DHCP requests? I know this is possible with ISC DHCPD (by allowing only requests from PXEClient vendor ids), but a nice windows GUI would be preferred.

Or if TFTPD32 can't do this, is there another equally easy to use piece of software that he can run on his Windows laptop? Since the TFTPD part is working fine, a DHCP server with the ability to serve PXE only would do.

Worst case I'll have to set up a virtual machine with ISC DHCPD, but I'd much prefer a small, simple solution.

I'm not interested in solutions that involve using the existing DHCP servers or separating machines on the network for deployment, the whole point is to be simple and stand-alone.

deployment dhcp pxe-boot dhcp-server tftp

5 Answers

  1. With the DHCP TAB of tftp32 you have to:

    Uncheck "DHCP Server";
Check "proxyDHCP";
Check "BINL";
Check "Bind DHCP to this address".

    Enjoy ;)

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  2. I don't think you can do this.

    The only viable workaround I see is disable the DHCP server altogether in TFTPD32 and just use it as the TFTP server. (I would do that anyway. 2 DHCP servers in the LAN is asking for problems.)

    But that would mean you will have your normal DHCP server specify the ip address of the TFTPD32 server to those clients instead of ignoring them. (You are already separating them so you know how to do this.)

    If the laptop can be in multiple subnets just give it a reservation in each one so you know which ip address to offer in each of those subnets.

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  3. Best Answer

    Just to close this, the simple answer here is that TFTP32D can't do this, or at least couldn't at the time. I ended up giving them a preconfigured VM image with ISC DHCPD and no access to the VM so they could only start/stop the thing.

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  4. I think that different DHCP servers can work on the same physical network under certain configurations. There are two ways to do that

    1. If you have a computer with ONLY one network-port, You'll have to:

      • Install VM first;
      • Fix the IP address of your VM into a DIFFERENT SUBNET than your original network;
      • Install Tftp32 on this VM 
      • Make Tftp32  DHCP server bind the network-port.

    2. If you can have TWO Network-Ports on the same computer, You'll have to:

      • Config different subnet for each network-ports;
      • Connect each ports to the same Switch;
      • Install Tftp32 and configure to bind DHCP to the port which is PXE subnet (mask must be different to you NORMAL DHCP).
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  5. It's not a "magic" flag, but a defined one, the DHCP discover includes options 60, 66 and 67 http://blogs.technet.com/b/dominikheinz/archive/2011/03/18/dhcp-amp-pxe-basics.aspx http://www.intel.com/support/network/sb/CS-028533.htm

    You could have the ISC DHCP server running in a VM on the technicians laptop.

    You could also use the Microsoft DHCP server to service PXE clients, and then if you wanted to restrict access use the pxelinux menu system with a password.

    If you used Windows Server on the laptop, you could run WDS and wdslinux on the laptop.

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