G'Day gang.

Just a quick question about network bridging. I live on campus and wanted my little linux box to be on the net at the same time my Laptop is. I wanted each to have their own IP address and have had success with this by testing it out with a switch in my room. Now I've decided since my little linux box has two NIC's, I'll just use it to bridge my network. In Gentoo, my net configuration looks like this:
#bridging
bridge_br0="eth4 eth5"

config_br0=( "dhcp" )

#stop our non-bridge interfaces from getting IP addresses
config_eth4=( "null" )
config_eth5=( "null" )

#we wish to access the WAN on our current machine
RC_NEED_br0="net.eth4"

This works fine for both parties, however, my bridge is now assigned a new IP address with each boot. I was hoping for it to keep the same IP address that the DHCP server used to assign eth4 to. The problem is that each time the bridge starts, a new IP address is given. (where as the DHCP server usually only issues one IP address per MAC address). What's the best way to accomplish a more constant IP address with my universities network setup? (static IP addresses don't work)