HP z400 (no network no Gigabit link NIC=BCM5764m)

[robinsmidsrod]

Try a packet trace (http://ipxe.org/howto/pcap) and see if you get unexpected responses to your DHCP requests. Make sure you trace on a place were you can actually see the packets, though.

I also notice you have a lot of RXE and some TXE, which could indicate some kind of network configuration error or misbehaving driver. Try to debug the undi driver (what you type in after DEBUG= is the name of some file from the source tree without the .c extension, separate multiple with just a single comma, no space, like this: DEBUG=scsi,iscsi).