Services

I have a pretty standard setup on a PC Engines box with a WAN interface getting it's IP via DHCP, and on the other end I have the m0n0wall DHCP server giving out IP addresses on the LAN.

This has been working fine for years, and still works fine for most of my machines, but one machine (an Ubuntu server box) now gets a DHCP lease from the WAN interface every time m0n0wall renews the external IP.
I have absolutely no idea how this can happen, or why it just started happening.

I have some suspicions about bridged interfaces on the Ubuntu machine being an issue (this is the only machine with that kind of setup), but I can't for the life of me figure out why it would be getting external IP's due to anything it could do on the LAN.  :/

Actually, it's not just DHCP traffic getting through to the LAN interface, setting a static IP on the Ubuntu server doesn't make any difference. The machine is temporarily completely moved to the WAN network every time the m0n0wall machine gets a new DHCP lease.