Someone just helped me through a bridging problem I was having, and I thought I'd throw the problem out to the list to see if it's a bug, or at least, for archival purposes. I have a machine that I'm using as a workstation, that I would also like to use to bridge a home LAN. It has two interfaces: bge and fxp. bge0 -> 172.19.206.56 fxp0 -> ipless When I bridged the two interfaces, the workstation could only talk on the bge side of the network, not the fxp side. Note that any device on either side of the network could speak to the other side. Some initial debugging: # sysctl net.link.ether.bridge net.link.ether.bridge.version: 031224 net.link.ether.bridge.debug: 0 net.link.ether.bridge.ipf: 0 net.link.ether.bridge.ipfw: 0 net.link.ether.bridge.copy: 0 net.link.ether.bridge.ipfw_drop: 0 net.link.ether.bridge.ipfw_collisions: 0 net.link.ether.bridge.packets: 2687590 net.link.ether.bridge.dropped: 0 net.link.ether.bridge.predict: 70 net.link.ether.bridge.enable: 1 net.link.ether.bridge.config: fxp0 bge0 # I tcpdump'ed on the fxp interface, and could see a device nab an address via DHCP, and an ARP to the device from my workstation seemed to work, but I could not ping it. It was pointed out to me that the fxp does off-board checksumming, and what would happen if I disabled the one on bge0? Well, it fixed the problem. I can have TXCSUM enabled *only* on fxp0, not on bge0: so long as TXCSUM is disabled on bge0, irregardless of the state of fxp0, I can talk to any device attached to fxp0.