Multi-part PXE boot not honoring next-server setting

Question

I'm trying to boot LynxOS via PXE. The vendor provides a NBP named pxe.0. I then configure and build an image called pxe.1. These are placed on the tftp server, which is not the same system as the DHCP server.

On boot, the system retrieves the correct information from the DHCP server, including the correct IP info, the correct next-server, and the correct boot file name. This has all been verified using tcpdump. There is no further DHCP traffic after this point.

The system correctly retrieves pxe.0, and then tries to get pxe.1, but fails.

I've determined that it's trying to get pxe.1 from the DHCP server, rather than the correct tftp server. I can verify this by placing the pxe.1 file on a tftp server on that system, and having to boot to completion.

My question then, is what is determining how the pxe.1 file is downloaded? Is the pxe.0 directing things at this point, and is making the poor assumption that the DHCP server is always the same as the tftp server, or is there something obvious I'm missing?

Answer 1

PXE roms are scary things. It would not surprise me to find out that it was using the DHCP server instead of the next-server setting.

You don't really have a whole lot of options here, aside from contacting the vendor.

You mention any hardware specifics, but perhaps you could replace the faulty 'pxe.0' rom with ipxe?

Answer 2

That's definitely a LynxOS bug; When your PXE boots performs a DHCP transaction getting its IP and the PXE parameters (TFTP IP and name of the NBP). The card PXE firmware correctly understand that the TFTP server IP is different than he DHCP server IP and correctly download PXE.0 (NBP). Once the NBP is loaded in memory should take the TFTP server IP from the PXE stack but it mistakenly takes the DHCP server IP as the TFTPs. You should report the bug and ask for a patch.