PXE - DHCP Options & IP Helper Missing

[dcanady55]

Hello,

My admin informed me he tried to setup a new PXE server with a new IP address and PXE failed. He set the new server's IP to be that of the old PXE server and the process started working again. I started looking into the situation only to find that there's no IP Helper configured with the PXE server on any device located in this building. Our DHCP server is located in a different building & different subnet and does not have any options configured for PXE. I am not a PXE expert by any means but from what I read you need to use either IP Helpers to point clients to the PXE server or have options setup on your DHCP to point to the PXE server. I have neither yet its working. What might I be missing? I did confirm PXE only works on this particular subnet.

Thanks

[paul driver]

Hello
You will require both for PXE boot,
1) Helper address to reach the dhcp sever
2) PXE options within the dhcp scopes to support pxe boot.

[dcanady55]

Hi Paul,

There is a IP Helper setup to hit our DHCP server but there's no options for this particular buildings subnet that has anything to do with PXE.

[balaji.bandi]

what was the IP address working one, and what is not working IP address,

did you added new IP helper address for pxe boot. also make sure VLAN have reachability to new PXE IP address ?

[dcanady55]

Hi BB,

The IP address of the new server was in the same subnet as the old server. I've captured a PC booting up at 3 places local client, PXE server and DHCP server. Inside the offer packet there is no relay agent IP on the PXE servers offer but there is on my standard DHCP server. Without a IP Helper directing those request to the PXE server or our DHCP server telling them where to go I'm not sure how its working yet. I've looked through every device config at this location for both helper addresses and the IP of the PXE server and there's nothing that points back to the PXE server. Our DHCP options are 3,6,15,44,& 46.

[balaji.bandi]

First we need to get what information configured on Layer 3 Interface helper address - what Option that mentioned have config on it.

Generally DHCP optuon 67  (other related used here)

check how the PXE works :

https://techcommunity.microsoft.com/t5/configuration-manager-blog/you-want-to-pxe-boot-don-t-use-dhcp-options/ba-p/275562

[dcanady55]

Hi BB,

I've read several articles similar to that one and I would agree IP Helper seems to be the way to go. There is not anything special in my configs pointing to the PXE server or any DHCP options on my equipment. My IP helper points all clients to our DHCP server which hands out those options I mentioned earlier. My capture from PXE server has no relay agent IP. Wouldn't there have to be an IP address there if there was a helper pointing to our PXE server?

[balaji.bandi]

Sure you can only what confiured there, we can only suggest based on the input

what is the OLD DHCP IP address what is new DHCP IP or PXE Server IP, this is very important for us.

what is the VLAN end device and IP try to contact DHCP and PXE ?