This article contains some background information to help you understand. If you want to skip to the main content, please go to the "How to determine if you need more IPv4 addresses" heading.

IPv4 addresses ("legacy IP" as we sometimes refer to them) are a limited resource. Back when the Internet was created, a 32-bit address seemed large enough. By doing some quick math, there are 4,294,967,296 possible IPv4 address values. 4 billion sounds large, but there are some addresses that cannot be used either for technical reasons or they are reserved (like carrier grade NAT or private addresses like what you use on your home or business network). This article won't get into all the technical details, but if you were to split IP addresses equally between all 5 global regions, you would be left with ~800 million per region. But some regions, like North America, are larger and therefore have more IPs than other regions like AFRINIC. Through the process of subnetting, or splitting up a larger network to a smaller network, you lose addresses (at least 3) for technical reasons. Because of this, IPv4 addresses are extremely limited and their use must be justified. 

Our policy has always been, and remains to be, that if you can justify addresses, they will be allocated to you. However, you must be able to justify them in a way where using name-based technologies (such as Server Name Indicator (SNI), port forwarding (NAT), reverse proxies, etc.) can't be used. For example, web servers can host hundreds to thousands of websites on a single IP address because of SNI and SSL certificates no longer require a dedicated port. You can also use a reverse proxy like NGINX or HAProxy to serve up websites and even some applications using SNI from a single IP address.

However, there are some cases where SNI doesn't work. For example: mail servers, DNS servers, and game servers are all port-based applications. It is impossible to run mail.nodespace.com:110 (POP3) and mail.example.com:110 (POP3) on the same IP address serving up both domains. This is a technical limitation and ARIN knows that and IPs will be justified in those situations.

How to determine if you need more IPv4 addresses

Ask yourself (or your administrator or application vendor) these questions:

• Does this work with server names?
• Can this work with custom ports (like moving SSH to 23, using 8080 for HTTP, 8443 for HTTPS)?
• Can I use a reverse proxy such as NGINX or HAProxy?

If you answered NO to any of the above, then you can probably justify more IP addresses.

Invalid Reasons That Will Be Denied

The following are a subset of reasons that additional IP addresses will be denied. It's not a fully inclusive list, but it is a helpful guideline.

• 1 website per IP (whether port 80, 443, or custom port) with the exception of appliance applications
• Outbound connections (the number of outbound ports will never exceed 1 IP, and if they do, you're probably in violation of our Hosting Agreement)
• SEO purposes
• IP pooling (you can have a pool of IPs, but you must demonstrate the rate at which you are using them for valid purposes)

This is not a fully inclusive list! Your request may be denied for other reasons. Our support team can assist you and answer any questions you have, especially if your request is denied.