It is possible to purchase additional IP addresses for a virtual private server, however you must have reasonable justification for the use of the additional IP address due to limited IPv4 space available globally.
There is currently only one justifiable reason for requiring an additional dedicated IP address: To set up multiple DNS Name Servers.
If you are setting up your own name servers, then you will need a dedicated IP for each. We can only supply single dedicated IP addresses or a block of 4 (/31). If you currently have a single IP and you wish to obtain more, you will need to have your primary IP changed as well (to a new block of 4). You must prove that your name servers will be registered within 30 days of issuance of the IP address otherwise the IP address will be revoked and you will be changed back to a single IP address again.
Please note that technically using multiple IPs for DNS hosting addresses is a weak justification because two or more IPs on the same block that route to the same server are likely to have the same failure rate as they're both in the same block and both hosted on the same server. Rather than using different IPs, you can instead simply map two name server addresses (ex: ns1 and ns2) to the same IP address. If you'd rather have the redundant (fallback) DNS services, you may wish to consider a cloud DNS service instead.
SSL certificates are no longer justification for a dedicated IP address as modern web servers use SNI to allow multiple certificates on a single IP address.
