Varnish quick install
Get varnish by installing keys
curl http://repo.varnish-cache.org/debian/GPG-key.txt | apt-key add - echo "deb http://repo.varnish-cache.org/debian/ squeeze varnish-3.0" >> /etc/apt/sources.list apt-get update apt-get install varnish
Setup rpaf so that apache will know about the original requesting client
apt-get install libapache2-mod-rpaf
Add the IP of the server to end of the following
nano /etc/apache2/mods-available/rpaf.conf