Bridged network only gets UDP broadcast traffic?

I've created a bridged network Mac OS X 10.8.5 using ifconfig and TUNTAP for OS X to bridge my wireless connection, en0, with a virtual interface, tap0, which I can use for guest VMs:

$ sudo sysctl -w net.inet.ip.forwarding=1

$ sudo sysctl -w net.link.ether.inet.proxyall=1

$ sudo sysctl -w net.inet.ip.fw.enable=1

$ sudo ifconfig bridge0 create

$ sudo ifconfig bridge0 addm en0 addm tap0

$ sudo ifconfig bridge0 up

$ ifconfig

en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500

ether 28:cf:xx:xx:xx:xx

inet6 xxxx::xxxx:xxxx:xxxx:xxxx%en0 prefixlen 64 scopeid 0x4

inet 192.168.100.64 netmask 0xffffff00 broadcast 192.168.100.1

media: autoselect

status: active

bridge0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500

ether ac:de:xx:xx:xx:xx

Configuration:

priority 0 hellotime 0 fwddelay 0 maxage 0

ipfilter disabled flags 0x2

member: en0 flags=3<LEARNING,DISCOVER>

port 4 priority 0 path cost 0

member: tap0 flags=3<LEARNING,DISCOVER>

port 8 priority 0 path cost 0

tap0: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1500

ether ca:3d:xx:xx:xx:xx

open (pid 88244)

I'm using this with QEMU and the guest VM never gets a DHCP lease. If I `tcpdump -i tap0`, I only see broadcast traffic. Shouldn't I see a mirror of everything on en0? (192.168.100.33, the host doing the broadcasting, is another unrelate, noisy server on my LAN.)

Any ideas?