WOL and Host OS discovery issues.


  • Hello all,

    Currently I am working on setting up a FOG instance for my company as they have been using macrium or an extremely outdated version of Ghost for image deployment prior to my coming on board.

    Currently I am having issues with WoL, packets are being sent out but are not being received. I assume this has something to do with how FOG handles DHCP, as both that and the Host discovery were working perfectly prior to shifting DHCP services over to the FOG server.

    The network is all managed by a Ubiquiti USG Pro, there are several V-Lans to segregate the network, however I only need WoL to work on one of those.

    FOG is running on Debian 10.10, a clean, headless install with nothing else running on it. I am just using the default FOG DHCP Server that it installs, but I can see that a lot of people prefer DNS Masque.

    My thought is that it is either the DHCP config on the FOG server or the way the VLAN is set up causing the issue?

  • Moderator

    @riry I’m glad to hear that everything is back in order in your house. The dnsmasq solution is a solid one in that you don’t have to mess with your existing infrastructure if your current dhcp server doesn’t support dynamic pxe booting. Secondly if you power off your FOG server so dnsmasq is off line so no pxe boot info is sent out. As soon as the FOG server is back online so is PXE boot support via dnsmasq.

    Well done getting everything working in your environment.


  • @george1421 WOL is now working as intended and DNSMasq is working a treat. I do not know why it was not working but the clients are now reliably receiving their packets since moving the DHCP server back to the Ubiquiti router. I can only assume there was some config stuff that I missed, but I am happy to run it like this.

  • Moderator

    @riry I have a tutorial for integrating dnsmasq into your FOG server here: https://forums.fogproject.org/topic/12796/installing-dnsmasq-on-your-fog-server

    Those instructions work out of the box if your target computers are on the same IP subnet/vlan as the FOG server. If your pxe booting computers are on a different subnet then you must do one thing. Add the FOG server’s IP address as the last server in your router’s dhcp relay/helper service. This way the FOG server’s dnsmasq will hear the pxe boot request.


  • @george1421 As I understand, WoL broadcasts to every IP address on the subnet to find a match for the MAC? I figured the DHCP server for some reason not behaving properly could have an affect on that, since I’ve tried sending magic packets outside of the FOG system on a few other VM’s or even the host machine now with no luck.

    The main reason I am not just using the Ubiquiti DHCP server is that I couldn’t get it to play nice with both EFI and BIOS boot over PXE at the same time, the hardware I have to work with is varied and not all the CSM settings seem to work universally. Shifting DHCP over to the FOG Server gave me more flexibility to have whatever hardware is needed booting off the network.

    I think I will give DNSMasque a try and see how that goes. Thanks for your help.

  • Moderator

    @riry said in WOL and Host OS discovery issues.:

    Currently I am having issues with WoL, packets are being sent out but are not being received. I assume this has something to do with how FOG handles DHCP, as both that and the Host discovery were working perfectly prior to shifting DHCP services over to the FOG server.

    I’m seeing WoL and dhcp being two isolated protocols. Actually WoL doesn’t use IP for communications, it sends out L2 packets using mac addresses and magic packets.

    I guess I would have to ask why you shifted from your previous dhcp server over to fog? There are valid reasons for doing this, but not typically in a functioning environment.

    If you moved it back, would WoL services return?

    If you have a current dhcp server that is working in your environment (maybe on a router or such) and it doesn’t support dynamic pxe booting then I would suggest dnsmasq, its a 10 minute setup with the configuration of dnsmasq I’ll recommend only supplying the pxe boot info only, the rest of the dhcp settings coming from your campus dhcp server.

    As host alive pings that maybe related to moving dhcp services to/where dns is no longer getting updated from dhcp. FOG relies on being able to resolve the host names in fog to IP address for the up/down check.

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