[geeks] Strange VLAN question

[Andrew Weiss]

I have a project where a customer has bought a set of switches and 
wants to isolate port traffic using VLANs for security purposes... 
unfortunately they need inter-VLAN routing, and they need access to the 
internet.  They HAVE no router.  Can one do untagged overlapped VLANS 
with one level of VLANS if one uses only one subnet... i.e. The WAN 
port is a member of all vlans, and then the other ports are members of 
only one vlan and the only thing that distinguishes them are non 
overlapping scopes of IP addresses on the same subnet.  So if 
192.168.1.7 is on VLAN 1, and 192.168.1.207 is on another... if one 
tries to ping the other they can't, however... if they both try to ping 
192.168.1.1 which is the shared port they'd both see it?

I know this reeks of bad style but I was wondering if this would work.  
I think tagging the port would make it unintelligible to the device on 
the other end (the router), but I'm not sure...

The switches are 3com... the router belongs to the ISP... Also present 
is a 3com NBX (on a separated VLAN with no connectivity required to the 
LAN for now), and two Cisco Aironet 1220's.

Thoughts?

My gut impulse is this might work but it would be screwy and bad style.

Andrew