I'm trying to set up my M0n0wall to support a LAN of PCs with NAT addresses, 
but to relay the DHCP requests from my set-top box to the specific DHCP 
server that my cable company uses for STBs.

I'm connecting my STB to OPT1 and have configured it to relay to the specific 
IP address of the DHCP server.  I can ping that server from the WAN 
interface, and if i spoof the MAC address then the WAN can pick up an IP 
address from the STB DHCP server.

But when I look at the server logs I think I find that the traffic is being 
blocked.

X [time]  	 STB  	 0.0.0.0, port 68  	 255.255.255.255, port 67  	 UDP

I have set up a rule to let all outgoing traffic from OPT1 go out, but not 
changed anything for incoming traffic on WAN.

Any advice on what could be happening?

HB