We've done nearly 100 at a time over two NetBoot servers on 1Gb switches. (4Gb Link from the switch the netboot servers are on) We've only tried that many as I've got this old max number in my head of 50 connections per server. At least that was the old default max on OS X Server was. We run two Mac Pro's and bound their ethernet interfaces together (trunked) to increase bandwidth and don't flood it with the 50/server limit. How many are you netbooting?

Academically I'd be interested to see how many people can do form a single server. Most institutions I know tend to prefer to spread out the load by installing multiple NetBoot servers/appliances across their network... or at least subnets in order to scale.

We have a Mac mini 2011 Server running 10.8.4 on a 1gig network and we have had 30 machines imaging at once. Granted it takes longer the more machines we have going at once since we usually only do 15-16 at a time. We are also looking at aggregating the thunderbolt port into another gigabit connection to help with bandwidth.

Gabe Shackney
Princeton Public Schools