Jeffrey Ollie wrote: [..]
But do the commonly-used operating systems support adding hundreds or thousands of addresses to an interface, and what would the performance implications be?
Remember that IP addresses are 128bits, while hostnames (the ones for the "Host:" header in the HTTP query) are well, quite a bit longer than that on average. If thus something like this would become common-place, there definitely will be quite some people who will be paying some attention on optimizing Apache. But yes, the network stack itself is a different question, then again, you can just route a /64 into the loopback device and let your apache listen there... (which also allows you to do easy-failover as you can move that complete /64 to a different box ;) Greets, Jeroen