Wondering if anyone has advice in this area:

We're looking to use multiple IP addresses to provide smart-card authentication to our Concrete5 sites. We're building in 5.7.5.13 with the intention to move to version 8 once we have permission and time to adapt our sites.
We will have up to 75 instances of concrete5 and can get any number of IPs, no problem.

Sample URL: MysiteN.org
Real URLs will not be numerically indexed
We would like to: Have anyone coming into
http://Mysite1.org
http://Mysite2.org
http://Mysite75.org
go directly to their webserver (up to 75 unique URLs, IE 75 unique IP addresses)

While anyone coming into
http://Mysite1.org/login
http://Mysite1.org/login
http://Mysite1.org/login
will have the organization smart card validated -
Good - continue to the webserver, where they log in to the backend
Bad - reject

The way the server is set up, we might have to use separate IPs for the proxies to let the web content managers in.

Can we do this with concrete5?

Any other ideas?