Hey gbaird,
A router is what gives you the ability to take private address space ex:192.168.1.0 and route it to the internet.
If I understood rcpettit correctly, he/she seemed to have one public IP address but has mutiple domains behind it(the public ip via the router).
If two requests from the internet both point to
http://public-ip.com the request comes in on port 80, unless you set-up a DNS record to change the port of one of the domains. If this is true, then both come to the public ip on port 80.
Set the router to point all
http://public.ip.com:80 to the SME server with ProxyPass installed, tell this server to point any DNS specific requests to one of the two servers.
Example:
Two domains: domain-one.com and domain-two.com, in DNS both point to Public Ip of 123.123.123.123;
Router Public Ip:123.123.123.123
Router Private Ip:192.168.1.1
First SME Server:192.168.1.2 is domain-one.com
Second SME Server:192.168.1.3 is domain-two.com
Set Router to Forward 123.123.123.123:80 to 192.168.1.2
Set up First SME Server with ProxyPass
Set up ProxyPass to forward domain-two.com requests to 192.168.1.3
This is my very simple understanding of this arrangement. I have used this set-up in the past. If anyone else can explain it better, by all means, please do.
Hope this helps
Joe