Can one SSL cover multiple domains?

Should your business need to secure multiple domain names or sub-domains, you might be able to achieve security using a single SSL. A Subject Alternative Name (SAN) Certificate secures multiple domain names on a single certificate. In most cases, a SAN certificate can secure up to 20 domains, however the domain names must point to the same hosting environment or the same IP address (normally used in a Shared Hosting environment).

Similarly, should you need to secure every sub-domain running off a single domain name, you can purchase a wildcard certificate.