What is a SAN? Sub Domain & Multi Domain Certificates Explained


A ‘Subject Alternative Name’ Certificate or better known as a SAN is a variation of SSL Certification that allows for more than just the one Fully Qualified Domain Name to be secured within the one certificate. Make no mistake, this is not a Wildcard Certificate. There are vast differences between the two.

Before reading on it should be noted that this explanation is referring to sub domain and multi domain CERTIFICATES and is not a detailed explanation of what a sub domain is. In the most basic form a sub domain is a domain that is part of the main domain. For example if the main domain name is ‘www.facebook.com‘, a sub domain would be ‘shop.facebook.com‘ as it is a smaller subdivision of the absolute domain name. Even though the domain name is longer, you are taken to a smaller subdivision of the main website and therefore is a sub domain. This article is an explanation of how to secure sub domains as well as completely different domains within the one certificate.

Securing multiple different domain names for the same organisation can become quite tricky. Having to re do the validation process over and over for a domain with a slight difference from the the original can become time consuming.  This is also the case when trying to install numerous different certificates onto domains that are kept within the one server as an SSL typically requires one IP per domain.

Choosing a SAN SSL Certificate can eliminate the hassle by securing vast amounts of different domains within the one certificate. The benefits include;

  • Reducing the time it takes to place almost duplicate orders. Eliminate having to place order after order.
  • Minimising the validation process and simplifying the renewal preparation.
  • Making SSL Management for a large amount of certificates easy by putting them under the one roof.
  • Eliminating the hassle in configuring multiple IP addresses on your server, binding each IP address to a different certificate, and trying to piece it all together.
  • Reducing the financial cost of purchasing numerous different certificates.

There are two types of SAN Certificates.

Sub-domain SAN.

A Subdomain SAN certificate has the ability to secure multiple different sub domain names on any level of the FQDN, as long as the root domain remains the same. For example, for ‘trustico.com’, the following domains can also be secured within the one certificate;

Multi-domain SAN.

A Multidomain SAN Certificate has the ability to secure multiple completely different domain names under the one certificate. There is really no limits in what you can secure. For example within the one certificate you could secure;

SAN Certificates that Trustico® offer:

  • Geotrust QuickSSL Premium (Subdomain)
  • Geotrust True Business ID (Multidomain)
  • Geotrust True Business ID + EV (Multidomain)
  • Symantec Secure Site (Multidomain)
  • Symantec Secure Site + EV (Multidomain)
  • Comodo SSL + Multidomain (Multidomain)
  • Comodo Positive SSL + Multidomain (Multidomain)
  • Comodo EV SSL + Multidomain (Multidomain)

If you are looking to secure your website(s) with a SAN Certificate please visit Trustico® for more information.

Image: Dailyhostnews

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