For reasons that are lost in the mists of time, our older Windows (2000, 2003) servers have been configured with a "Administrative" IP address and three further "Hosting" IP addresses. There are also additional IP's for sites with SSL certificates.
The "Administrative" IP address is where all our internal provisioning, monitoring and other such apps are bound to. We lock this down and don't permit access to it from the outside world (other than over our VPN).
The three "Hosting" IP addresses are used for IIS website hosting (in conjunction with host headers).
Historically, new site IP address allocations have been rotated through these three IP addresses. I'm not really sure why.
I'm building a new batch of servers and I'm considering just having a single hosting IP address.
Our servers can host up to 1200 sites on a single machine.
Is there a technical limit to the number of IIS sites that can bind to a single IP address? Our Linux platform seems to do just fine with just a single shared IP + host headers.
I initially thought this might be an SEO thing, but given that IPv4 address space conservation is paramount I hardly think Google or other search engines could reasonably penalise site rankings just because hundreds of sites hang off the same IP.
Best Answer
From a (now broken) IIS FAQ at TechNet:
It doesn't sound like there's a real upper limit to the number of host header sites you can have, but I've yet to find any hard evidence.