Virtual Host Monster and Load Balancing

Plone Support Administering Plone sites
2

I think I don't understand your problem; you have to give more information on what are you using to serve your site and do load balancing.

load balancing can be done in many ways involving nginx, Varnish, HAProxy… and so on.

here is an example on how to do that on nginx:

upstream plone {
    server 127.0.0.1:8081;
    server 127.0.0.1:8082;
}

server {
    listen 80;
    server_name www.example.org;
    location / {
        proxy_pass http://plone/VirtualHostBase/http/www.example.org:80/Plone/VirtualHostRoot/;
    }

usually when I want to connect to one specific instance I point my browser directly to its IP address and port.