siehe: Understanding TUN TAP Interfaces

Nur TAP (OSI/ISO-Layer 2) kann in einer Bridge verwendet werden, nicht TUN (OSI/ISO-Layer 3)!

https://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/network-bridging.html

Brücke anlegen:

> ifconfig bridge create
bridge0

> ifconfig bridge0
bridge0: flags=8802<BROADCAST,SIMPLEX,MULTICAST> metric 0 mtu 1500
        ether 96:3d:4b:f1:79:7a
        id 00:00:00:00:00:00 priority 32768 hellotime 2 fwddelay 15
        maxage 20 holdcnt 6 proto rstp maxaddr 100 timeout 1200
        root id 00:00:00:00:00:00 priority 0 ifcost 0 port 0

an die Brücke 2 NICs anhängen:

# ifconfig bridge0 addm fxp0 addm fxp1 up
# ifconfig fxp0 up
# ifconfig fxp1 up

/etc/rc.conf:

...
ifconfig_tap0="192.168.1.213/24"
ifconfig_tap1="192.168.1.214/24"

autobridge_interfaces="bridge0"        # List of bridges to check
#autobridge_bridge0="tap* vlan0"       # Interface glob to automatically add to the bridge
autobridge_bridge0="tap*"              # Interface glob to automatically add to the bridge
...