In this article, you will learn about SNI and Zimbra SNI. It would be important for you to set up Zimbra SNI as you can serve your users not being worried about the number of limited IPv4 addresses per domain. So let’s take a look at How to setup SNI in Zimbra OSE?
What is SNI?
If I want to run several HTTP websites on a single IP address I can use different hostnames for them, so when a user requests to connect to one of my websites, it simply uses a unique HTTP header including the hostname, then my server checks the header and connects them to the requested website. Although this scenario works perfectly, it does not work on HTTPS, since in this protocol the server cannot see the information in the HTTP header as it uses the SSL or TLS method. Before introducing SNI, I should have purchased a different IP address to have a certificate for each which translates to more cost. The other problem is that IPv4 addresses are limited (around 4 billion), which with the introduction of Server Name Indication (SNI), there is no need to purchase several IP addresses since it allows multiple certificates hosted on any IP address. SNI uses the fact that by including the HTTP header (virtual domain) in the SSL/TLS handshake, the server can see the virtual domain and will provide the user with their request.
Zimbra SSL SNI offers multiple SSL certificates on just one IPv4 address by allowing the proxy server to provide several certificates on the same IP address. It allows multiple HTTPS secure domains exist on the same IP address not using the same multi-Domain SSL certificate. Zimbra SNI can be important for providers hosting thousands of domains not being worried about the number of limited IPv4 addresses per domain. Zimbra SSL SNI is included in Zimbra 8.7 and above makes it possible to protect more Domains by using fewer IPv4 addresses.
Browser support for SNI
To make use of SNI, as with any protocol, the majority of visitors must use web browsers that support it. Almost all the current browsers support SNI.
SNI setup on Zimbra
To set up Zimbra SSL SNI you can read this How to setup SNI in Zimbra OSE?