You could just install apt-cacher-ng on one of the machines and have all the other ones (*and* the one with apt-cacher-ng) configured to request packages through that machine.
The first machine being installed will fetch them on the Internet, all the other ones will fetch them from the apt-cacher-ng system.
You can test this with smaller packages to make sure your setup is right.
It basically consists of:
- On server system:
** configure it with a static IP address (let's say it's 192.168.1.10)
** sudo apt-get install apt-cacher-ng
** visit
http://localhost:3142 to make sure the setup is OK, a web page should show up with stats and info.
- On all server + client systems:
** edit /etc/apt/apt.conf.d/02proxy as admin, add a line to refer to the server:
sudo nano /etc/apt/apt.conf.d/02proxy
the line is:
Acquire::http::Proxy "192.168.1.10";
** On any machine (INCLUDING SERVER):
sudo apt-get update && sudo apt-get install cheese
should install cheese at usual download speeds
** On any *other* machine (INCLUDING SERVER):
sudo apt-get update && sudo apt-get install cheese
should download cheese at much higher speed (ie. your LAN's).
Perhaps also try installing inkscape or a bigger package to measure speeds, etc.