"Ethernet doesn't scale because of large amounts of broadcast traffic."
We started to introduce multicast, and multicast-aware switches in IPv4; in IPv6 there is no broadcast traffic. We won't be able to scale networks up until we can turn off IPv4,
In other words, probably not for another decade at least?
but once we can IPv6 will be able to grow much larger in terms of per-LAN. The best practice of no more than 512 per broadcast domain will seem very outdated at that point; especially when you add in multicast flood protection, the available bandwidth goes up, and performance of network interfaces improves.
Yes and no. If you remove the broadcast traffic you can *in theory* scale higher. However, this does nothing for the difficulty of L2 troubleshooting, which is a real problem in large flat L2 networks.
The link you pointed to is talking about flat networks of tens of thousands of hosts; that might be excessive right now... But I can certainly see an IPv6-only LAN (with some filtering to make sure ARP and IPv4 traffic is dropped at the port) scaling easily to thousands of hosts with today's hardware.
I'm afraid I remain sceptical, unless we come up with significantly improved methods for L2 troubleshooting. Steinar Haug, Nethelp consulting, sthaug@nethelp.no