> -----Original Message-----
 Since CA will make you log in after the 
> mac-address to ip-address combo is void(dhcp lease time has 
> expired and the user receives a new ip, user moves to another 
> subnet, etc)

One note,
DHCP will always give you the same IP you had, unless something forces
it to change. (New subnet, new Client ID (Mac address, OS)

So I just wanted to point out that it's quite conceievable that with
that setup, your students will never logout, unless you clear the
certified device list.