Configuring VLANs - Why is IP address require on NIC connected to Trunk?

[Wojciech Puchar]

> done using ifconfig_em0_name="ext0" in rc.conf.
>
> I find I have to give the ext0 interface an IP address in order for routing
> and packet filtering to work on the attached VLANs.

You have to set up IP address to vlans, not main interface. It's the way 
vlan's work.

Having 2 vlan's is like having 2 ethernet cards, while physically having 
one. switch is responsible to segregate your traffic and connect one 
"virtual ethernet" to right clients, and second to other clients - exactly 
how you configured switch.