Some hosting providers offer dedicated IP as a option in addition to shared hosting. In case of virtual or hardware server it is the must, but is it really needed when hosting is shared between clients?
When browser request some document from server over HTTP protocol, it pass several parameters to describe what exactly does it want to get. The major parameters are IP address of the server and port number (usually it is fixed for HTTP protocol and equals to 80). Those two are used to establish TCP connection. The problem was that it was needed to have a separate server per every website. Than HTTP protocol was updated. A new parameter was added (host name). It is not mandatory, but used to identify which of sites is requested by the browser from the shared server.
So it seems that everything became fine, but Internet gets larger and it’s needed to encrypt connections because servers became more complicated. In our days sites not just spread public information, but also allow authorized access. HTTP is fine for public information, but private data should be encrypted and that’s what for HTTPS appeared. HTTPS is just HTTP wrapped with SSL.
The new problem was that SSL protocol does not specify host name and in order to workaround it, a dedicated IP address was needed. And this problem does not come alone because number of IP addresses is limited.
So is there a solution for all of that? Fortunately yes! The solution is Server Name Indication (SNI). In case both server and browser supports SNI, it becomes possible to use shared IP address for multiple HTTPS sites.
But does browsers support SNI? What’s about compatibility? – may one ask me. Well, starting from April 2015 (after Windows XP retired) all the modern operating systems and browsers support SNI, so it is absolutely safe to use shared IP for SSL in our days.
However there are some cases when purchase of dedicated IP address make sense. There are several reasons for that, for sample support for legacy Windows XP clients. Also search engines like Google, Yahoo, Bing, etc. take into account how much sites are hosted in a single IP address. Many sites at single IP is a sign of cheap shared hosting and theoretically could make site’s rank lower.
My recommendation for sites with less than 10k visitors per month: don’t waste time and money on dedicated IP. Ensure your hoster support SNI and does not require to purchase dedicated IP for SSL certificate installation.