Thanks everyone for the support.

@Daniel-Miller and @Sebastian-Roth I opted for the approach you suggested of making TFTPD ‘correct’ the filenames. The affected PC now goes to the FOG menu. I missed Sebastian’s map file and ended up writing my own which is:

# Workaround for PXE clients that misinterpret the DHCP options
# because they expect a null-terminated string

# match the extensions followed by any characters and replace it with
# just the extensions

r \.pxe.* \.pxe
r \.ipxe.* \.ipxe
r \.kpxe.* \.kpxe
r \.kkpxe.* \.kkpxe

@george1421 I wouldn’t even have guessed that proxy DHCP was a thing. I’ve decided not to go for it this time but I’ll keep it in mind for future.

67_68_69_4011.pcap

Since the pcap I ran earlier captured everything, I’ve filtered it to cover ports 67, 68, 69, 4011, and uploaded accordingly. (I can send the entire capture privately if you need it; since I don’t know what information might be in it I don’t wish to post it publicly). It looks like you’re right that option 67 in the DHCPOffer and DHCPAck isn’t null-terminated though.

The Unifi Security Gateway runs EdgeOS which is a fork of Vyatta, and can run either ISC DHCPD or dnsmasq as the DHCP server. (There’s an option to select which but I can’t find it at the moment). If any of that helps.

For the PC, I updated to the latest BIOS. On Dell’s support site there’s no specific NIC firmware for this model that I can find. I guess I can see if Windows update turns up anything.

Hi all,

I’ve recently got a FOG server up and running and am having problems with some models of computer failing to PXE boot. (Specifically, Dell Vostro 220, which the wiki reports as working). I’ve had other models of computer go to the iPXE menu no problem.

On the affected PC the error is

PXE-T01: File not found
PXE-E3B: TFTP Error - File Not Found
PXE-M0F: Exiting PXE ROM

Doing some digging, I ran a pcap on the FOG server’s host, and discovered that for the affected computer model, the source file name in the TFTP read request has a bunch of garbage bytes appended to it, which are not there for the computers that behave normally. I have attached an excerpt of the packet capture, showing first the TFTP traffic for a “good” computer, trimmed after the first data block, and after that the traffic for the “bad” computer.

Our environment is DHCP provided by a Unifi Security Gateway, FOG running in an Ubuntu 18.04 LXC container on Proxmox.

I updated the affected PC to the latest available BIOS and that didn’t help.

How can I resolve this problem? The idea that comes to my mind is to make a copy of undionly.kpxe named to match what the computers are requesting, but that seems like a kludge and I’m wondering if there’s any better way.

excerpt.pcap

(PS: It seems like every packet is quadruplicated in the capture. I think that’s just a quirk of running tcpdump on Proxmox, I probably used the wrong tcpdump options.)