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***NiKiZe*** · 2018-12-28, 01:49

(2018-12-28 01:40)luis84 Wrote: Thank you both. So my config was indeed bad but the issue is actually bigger, you see, my modem is also acting forcefully as a DHCP server (because it has router functionality) and this was replying to the DNS requests in addition to my PXE server. I discovered this with wireshark (as suggested above)... it became evident quickly. Normal PXE is grabbing the right gateway and then loading the iPXE chainload but then iPXE is grabbing the details from the incorrect DHCP server.

As a result the second and final request for the file is replied to by both my ISC-DHCP and my modem's DHCP, and even though ISC-DHCP is set to authoritative, it's not given priority. I did not have this issue with DNSMasq because it was running as a ProxyDHCP which is something that ISC DHCP will not do. For other reasons I need to use ISC DHCP so for anyone with this issue, if you've got a DHCP server on your network then you can't just add a second DHCP server in the same subnet. You can use DNSMasq to handle the DNS Requests set to ProxyDHCP and it'll work fine with iPXE.

If you need to use another DNS server without ProxyDHCP support such as isc-dhcp then the best option appears to be using an embedded script in the chainloadable iPXE file which then does not even require a DHCP replies to proceed. This is the route I am currently taking, it seems like a far superior way to truly harness iPXE anyway!

Thanks everyone.

I think you are missunderstanding how DHCP works, (or is intended to work)
You should only have one DHCP server on a network, If you have more then the result will be undefined. In practice it becomes the first received response that will be what is used, so a faster machine will be more likely to have its sent DHCP lease be used, rather than a slow router.

Also don't mixup DNS with DHCP, dnsmasq happens to do both, but that is the only one that does AFAIK.
DNS is for name service and has nothing to do with DHCP (except for many DHCP servers updating DNS records when giving out a lease)

In your case you should make sure that the DHCP server in your router is disabled. In most routers this is possible to change, and still have it act like a router.