Here's a weird problem.

We've got a number of devices with dual-NIC mainboards. Some are Realtek NICs, which suck. Some are Intel e1000s, which don't.

I've just noticed on 2 machines, one is an Intel NIC, one is a Realtek, that when I put the MAC address of one machine into the dhcpd.conf file on our DHCP server to get it to PXE boot the machine into a rebuild environment, initially everything is fine.

The server gets a DHCP allocation, and PXE boots into the Ubuntu preseed enviroment.

On one or two machines, it gets as far as Ubuntu's DHCP network configuration, and fails. If i pull up a busybox shell (on tty2 on the installing machine), and run ip link, I can see that the UP flag is set on the other NIC.

Here's some stuff.

  host xeon16-ghz240-gb48-node1 {
        hardware ethernet BC:AE:C5:07:1F:18;
        filename "pxelinux.0";
        next-server 192.168.123.80;
  }

That's what's in dhcpd.conf

This is what ip link on the evil machine looks like.

Only one NIC is actually connected (deliberately).

As you can see, the NIC that's in the dhcpd config, is not marked as UP, and the link that is UP, isn't the one in DHCP.

So far I've seen this on two brands of dual-NIC configuration.

Does anyone know 1) what's causing it, and b) What we can do about it?