Isolating wired and wireless clients

[jjacobs13]

I am trying to determine the most effective (and cost-efficient) way
to isolate wired and wireless connections on the following setup:


I currently have a building with 15 ethernet connections to the
Internet. At three of the locations, a wireless router (Linksys
WRT54G v8) will be used to:

1. share the network connection via ethernet with two computers

2. provide wireless connectivity


I am not concerned w/ wired computers communicating with other wired
computers. But I do not want any communication between wired and
wireless computers. Any good ideas would be appreciated. Thanks.


Solutions that I have dismissed:

I believe the Linksys WRT54G v8 does not have native support for
VLANs.
(Perhaps an alternative firmware like dd-wrt? I believe this would be
one of the easiest solutions, but I worry about installing third-party
firmware and, in the future, leaving it in another person's hands that
isn't familiar w/ such.)

I could buy another router for each and utilize double NAT, but that
would be another $150+ (not including deals) and could - or so I've
heard - limit some services (most notably VPN?).


I am open to suggestions about securing the "post-NIC" side of the
connection, but I would prefer to plug & go without extra
configuration (e.g. static IP w/ software firewall).


Also, any additional resources/web sites for further clarification or
explanation would be appreciated.

 

[jjacobs13]

I forgot to mention the connection sequence:

Cable modem <---> Cisco ASA 5505 <---> Switch (undetermined) <---> 15
ethernet ports

 

[jjacobs13]

I forgot to mention the connection sequence:

Cable modem <---> Cisco ASA 5505 <---> Switch (undetermined) <---> 15
ethernet ports

 

[jjacobs13]

I forgot to mention the connection sequence:

Cable modem <---> Cisco ASA 5505 <---> Switch (undetermined) <---> 15
ethernet ports