I have a bridge(4) here with some epair(4)s and an ix(4) (Intel X520). When I add or remove the first vmnet(4) member the bridge flaps. I can see no reason why it should do that. Once the bridge already has a vmnet member, I can add and delete as many vmnet interfaces as I want, without it flapping. My workaround is to add a dummy unused, vmnet999 to the bridge in /etc/rc.conf to get the flapping over with. But surely that cannot be right ? I noticed that vmnet(4) is the only interface with IFCAP_LINKSTATE, and that bridge_linkcheck() is interested in that bit, but I would pressume that the other interfaces being LINK_STATE_UP will keep the bridge up in the hasls==0 case. I'm not going to be very popular if I muck too much about with this machine particular, so sticking prinf's in there is not at present an option for me.