3 NICs - 1 upstream, 2 downstream to same subnet??

[rip]

Hello All;
 Here is the puzzle

Config  : 5.1-Release
3 xl interfaces   xl0, xl1, xl2

I am trying to make a configuration to isolate the WiFi APs on a single 
segment. DHCP hands out 'good' addresses (10.0.0.x) to MACs it 
recognizes and 'bad' (10.99.0.x) when the MAC does not match and is 
taken from the common pool.
I then will use ipfw to block the trespassers, but do a bit of data 
collection at the same time. I don't expect much bad traffic here since 
WEP will keep out the casual. Just a defense-in-depth thing.

I have the upstream interface on xl2  no problem;
I want to have 2 segments of  10.0.0.0/8 on xl0 and xl1

--pseudo commands)--

ifconfig xl2 inet 198.162.1.1                                     
//upstream router
ifconfig xl1 inet  10.0.0.254  netmask 255.0.0.0     // this box = 
default router + all wired machines
ifconfig xl0 inet  10.?.?.?        netmask 255.0.0.0    // Wifi AP 
segment + all wifi connections

--ipfw--
  deny ip from 10.99.0.0/16 to any in via xl0          // block trespassers

??  Is this possible?
??  What sort of ip address should xl0 have. When I gave it a 10.99.0.0 
255.0.0.0 address, the netstat -rn said all 10 traffic was on xl0, whicj 
was not true.
??  Will the OS route traffic comming in on xl0 (with good ips) throug 
the stacks to xl1 and then on to xl0 for external traffic.
??  Will this act as a switch (mac specific) or a hub (broadcast mode).


  I have had problems with multiple interfaces if this type (xl). I 
found that I had to insure all interfaces were down as each one was 
configured. If another xl interface is up, an error message is returned 
about an existing file.


Rip Toren