[CentOS] Centos as Gateway ? (Router/transparent proxy)

  Hi All,

I'm lately suffering from Quota abuse at home. believe it or not my 
teenagers are eating through my allowed quota.

Hence, i'm thinking of setting up a centos machine to work as such:

HDSL modem(natted to an onboard dhcp service for lan users) -> Centos - 
 > Switch - LAN users


Hw specs:

3 GB ram
3.0 core 2 duo
2 X 1 TB HDD
2 X 1 Gb NIC


Centos will contain the following:

     1. DHCP # is there a way i could use the modem's dhcp service 
instead? or using a centos based dhcp service is better?
     2. Samba # sharing files for lan users
     3. Squid
     4. clamav
     5. OpenRadius # wifi authentication
     6. knockd service (anyone tried it? i read about this service a few 
weeks ago and am wondering if it's worth giving it a shot... for public 
access to the server )
     6. Things which are needed :
             a. Ability to separate Wireless router from LAN. (thinking 
of vlans though as i have a dumb switch am thinking of adding a 3d NIC 
to my desktop and dedicating it to the wifi ? )
             b. Accountablity of quota and bandwidth used (i was 
thinking of SARG and SQstat for squid)
             c. using some sort of shell script that will parse squid 
logs (mysar will help me access squid logs through mysql) and if someone 
bypassed their allowed quota for the day they will be moved to a delay 
pool with lower bandwidth.

As you noticed above, my whole "connection management" is relying on 
squid,  i'm worried that it will process only traffic that's forwarded 
to port "80" instead of everything going through the server. any idea if 
thats the case?


I previously thought of untangled, and IPCOp, though i don't want a 
standalone router as i'd like to be able to use VirtualBox over it 
occasionally.
waiting for your advice about the above setup, keep in mind that i don't 
mind changing the setup if there's something better to use, actually i 
do prefer it.

Best,


--Roland