Do subdomains need certificates?
Yes, in general, a different SSL would be required for each subdomain, because each subdomain is considered a separate domain. However, there are wildcard SSL certificates available on the SSL market. To secure all subdomains of your domain, you will need to get a Wildcard SSL certificate.
Why would you deploy a wildcard certificate?
A wildcard certificate is a public key certificate used by all subdomains within a larger domain. Using a wildcard certificate on a publicly facing web server, you can quickly secure unlimited subdomains that are all encrypted by the same certificate.
How to secure multiple subdomains with single SSL certificate?
Following are the types of subdomains and domain a wildcard SSL can secure: A Multi-Domain Wildcard SSL certificate can secure multiple domains and subdomains. This SSL certificate works like a Wildcard SSL certificate and a Multi-Domain SSL certificate. You can protect multiple FQDNs and all their subdomains at all levels.
What kind of certificate do I need for multi-level domain?
Here’s what I need to secure: Any combination of city.state.foo.com. (These are US states.) My understanding is that a wildcard certificate can only cover one “level” of subdomain. According to RFC 2818: Names may contain the wildcard character * which is considered to match any single domain name component or component fragment.
Can a wildcard SSL certificate be used for unlimited subdomains?
A Wildcard SSL certificate is marketed as being able to secure “unlimited subdomains” and that’s partially true but with the caveat that all those sub-domains must be at the same level of the URL. And generally, that’s not a problem. But with companies that make use of multi-level subdomains in their web architecture, it can be.
When do you need to secure multiple subdomains?
It can get complicated when you need to secure multiple websites across different subdomains, or across multiple levels of subdomains (for example: blog.domain.com and new.blog.domain.com). Before we jump into analyzing more advanced scenarios let’s start with a short summary of standard wildcard SSL certificates and how they work.