PXE and IP Helper Configuration

John Burris 1 Reputation point
2021-11-20T22:37:25.807+00:00

Hey Everyone,

I have searched for an answer for some time without success - or maybe I just didn't understand it when I found it. We are trying to get PXE working using IP Helpers in the following scenario.

  1. DHCP server is at a remote location on a different subnet from both the WDS server and the client. There are IP Helpers in place for the DHCP server and DHCP is working.
  2. WDS server is on the same subnet as the client.
  3. The client is connected to a switch. That switch is uplinked to a master switch which is then connected to the router. The WDS server is connected directly to the Master switch.

DHCP is working with the IP Helpers in place for it and we have been successful PXE booting using the DHCP options 66 and 67 - that works fine. If we remove the DHCP options PXE no longer works which is expected. We then followed the guidance here to add IP Helpers to the router for the WDS server and UDP 4011:

https://www.manishbangia.com/ip-helper-address-configuration-for-pxe-boot/

After making tis change we attempted to PXE boot and nothing happens - the client just sits there doing nothing. Is there something obvious we are missing here? Do we need IP Helpers if the WDS server is on the same subnet? Do the IP Helpers need to be on the switches instead of the router? Do we need something else set on the DHCP or WDS server?

Feels like the solution might be a simple misunderstanding on our part but can't put my finger on it.

Thank you.

John

Windows 10 Network
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Windows DHCP
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Windows: A family of Microsoft operating systems that run across personal computers, tablets, laptops, phones, internet of things devices, self-contained mixed reality headsets, large collaboration screens, and other devices.DHCP: Dynamic Host Configuration Protocol (DHCP). A communications protocol that lets network administrators manage centrally and automate the assignment of Internet Protocol (IP) addresses in an organization's network.
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  1. Limitless Technology 39,201 Reputation points
    2021-12-15T19:11:19.457+00:00

    The routers must be able to route the client requests from the network of the client to the network of the DHCP server. One such simple router rule is the IP helper. The helper just tells the router to forward the DHCP requests to the known IP address of the DHP server.

    For PXE requests, you just need to configure the routers to forward the client request to the PXE server, just like you do with the DHCP server. Locate your router, find the DHCP IP helper entry, and add another entry that looks exactly like the first one but uses the IP address of the PXE server. For more information, see the blog post You want to PXE Boot? Don't use DHCP options.
    https://techcommunity.microsoft.com/t5/configuration-manager-blog/you-want-to-pxe-boot-don-t-use-dhcp-options/ba-p/275562

    Besides, you can add an IP helper entry for each PXE server. In a load-balancing scenario (multiple PXE servers), PXE servers can be up or down in a group, and you don't have to do any extra configuration. In diverse environments (Windows, Linux, and Router PXE servers all coexisting), the different PXE servers can selectively respond to the clients that they recognize.

    https://learn.microsoft.com/en-us/troubleshoot/mem/configmgr/boot-from-pxe-server

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