Ok, so I'm hoping the answer to this question will complete my basic
understanding of vlan setups.  I have a system with the following
network device configurations:

---------------------------------------------------------------------
hostname.dc0: up

hostname.vlan0: inet 172.17.1.1 255.255.255.0 172.17.1.255 vlan 512 
vlandev dc0 vlanprio 1

hostname.vlan1: inet 172.17.2.1 255.255.255.0 172.17.2.255 vlan 513 
vlandev dc0 vlanprio 2

hostname.vlan2: inet 172.17.3.1 255.255.255.0 172.17.3.255 vlan 514 
vlandev dc0 vlanprio 3

hostname.vlan3: inet 172.17.4.1 255.255.255.0 172.17.4.255 vlan 515 
vlandev dc0 vlanprio 4
---------------------------------------------------------------------

Now, in order to get hosts plugged into the switch that attaches to
dc0 to see their respective vlan device as a gateway they all have to
be configured with a vlan device as well, or else the switch itself has
to support vlans in hardware?  Or is there a way to do this with packet
filter so that neither the hosts nor the switch require a special
configuration?

Sorry I feel really dumb for not being able to figure this out from
the existing documentation.  Perhaps I've missed out on some of it?