We've got a few WRT devices from Linksys here, and the issue has arisen to deploy them in a relatively small environment, However, in the interest of manageability we'd like to be able to automatically VLAN (ideally NOT subnet) every user from one another. It seems obvious to me that the default firmware isn't capable of this - can OpenWRT/Tomato/DD-WRT support any sort of functionality such that new users are automatically VLANed or otherwise logically separated from other users? It seems like there's an easy IPtables or PF solution here, but I've been wrong before.
(If that seemed a little ambiguous, heres an example)
User 1 sends DHCP request to server, new VLAN (We'll call VLAN 1) is created, user is placed in that VLAN. Then, user 2 sends a DHCP request and is placed in VLAN 2 etc. etc.
i think what you are after is 'Client Isolation Mode' - ddwrt supports it. all users will be in same vlan but they will not be able to communicate one with another on layer2.