The software manager section is not going to work, I'm afraid - it needs to be able to see the outside world - so you'll need to manage these machines manually.
Which keys have you imported into the downstream servers? For this to work you need to export the "source" server's master repository public key, and import that to each of the downstream servers.
I exported the Source servers Local Master Repository Public Keys for both 1024 and 2048 bit.
That should be enough What happens when you try to pull from the source site? Any errors in the epoapsrv.log?