PXE with IP Helpers/DHCP Relay

[pmj000001]

I'm a Sysadmin and I have a question about what is best practice in regards to PXE servers. We are currently using DHCP Options for PXE clients (options 66,67). This works for most clients but is not the recommended method from either of the vendors we have used (Microsoft or Symantec). They recommend using IP Helpers / DHCP relay to forward the DHCP discover request to the PXE servers so that the PXE server is getting the actual request. This is more of an issue now with UEFI-based machines where the boot file would be different based on if the client is UEFI.

My Network team is against using IP Helpers and thinks it can cause issues. This doesn't seem to make much sense to me, as from what I understand, all that happens is both the DHCP server and the PXE servers get the DHCP discover and respond with their relevant info. Can someone clarify what, if any, issues there are using multiple IP helpers/DHCP relay with PXE Servers like SCCM & Altiris? Is this not standard practice?

[pmj000001]

This will work for the most part, but like I mentioned in my original post, you need the PXE server to see the actual request and not use DHCP options for imaging UEFI machines (of course on many PCs you can switch them to legacy/BIOS compatibility, but Surfaces and other machines are only UEFI).

[KimmyMuma]

Nothing is "ludicrously old" if it keeps coming up and biting you in the a**... Was having the same problem lately with where to place the IP helpers command. We have local Cisco DHCP servers provided by routers (3945s) where the VLANs are described/SVI'd (no VTP here). I was putting the "ip helper" statement on the SVI interface, at the router ... which is not where the initial client broadcasts are being received (which is at the switch).

We had been trying to get SCCM client provisioning (imaging) going for a while, with client and SCCM on different subnets, and DHCP being offered on the local client subnet.

Was getting nowhere until I discovered that the "ip helper" statement had to be on the SVI interface (pointing to SCCM address, on a different subnet/VLAN) on the switch ... Maybe you guys already knew this, but it took me a couple of days.

In summary:
- DHCP requests on/from router, servicing the to-be clients, on a switch;

- SCCM on different VLAN/subnet;

- "ip helper-address" on the VLAN definition, on the client-facing switch, pointing to the IP address of the SCCM WDS server;

BTW - still didn't work (machine gets an IP, downloads and runs the PXE boot, then requires "authorization from WDS), but now a Windows server admin issue, and off my book ... :-)