Great guide here – http://www.classhelper.org/articles/reverse-proxy-server-squid-debian/installing-squid-proxy-server.shtml
I’ve modified slightly for Ubuntu, but almost identical.
apt-get install squid
cp /etc/squid3/squid.conf /etc/squid3/squid.bak
rm /etc/squid3/squid.conf
nano /etc/squid/squid.conf
http_port 80 defaultsite=www.yoursite.com vhost
forwarded_for on
refresh_pattern ^ftp: 1440 20% 10080
refresh_pattern ^gopher: 1440 0% 1440
refresh_pattern . 0 20% 4320
cache_peer 192.168.0.13 parent 80 0 no-query no-digest originserver name=web1
acl sites_web1 dstdomain www.yoursite.com yoursite.com
cache_peer_access web1 allow sites_web1
cache_peer 192.168.0.14 parent 80 0 no-query no-digest originserver name=web2
acl sites_web2 dstdomain www.anothersite.com anothersite.com
cache_peer_access web2 allow sites_web2
acl all src 0.0.0.0/0.0.0.0
acl manager proto cache_object
acl localhost src 127.0.0.1/255.255.255.255
acl to_localhost dst 127.0.0.0/8
acl SSL_ports port 443
acl Safe_ports port 80 # http
acl Safe_ports port 443 # https
acl Safe_ports port 1025-65535 # unregistered ports
acl CONNECT method CONNECT
http_access allow sites_web1
http_access allow sites_web2
http_access allow manager all
http_access allow manager
http_access deny !Safe_ports
http_access deny CONNECT !SSL_ports
#http_access deny all
access_log /var/log/squid3/access.log
cache_mgr [email protected]
Modify your hosts file to include web1 and web2
nano /etc/hosts
192.168.0.13 web1
192.168.0.14 web2
Another good article about benefits of reverse proxy
http://2bits.com/articles/increasing-drupals-speed-squid-caching-reverse-proxy.html