【My Study Note】Non-Routable Address Space
Non-Routable Address Space
Even as far back as 1996, it was obvious that the internet was growing at a rate that couldn’t be sustained.
When IP was first defined, it defined an IP address as a single 32-bit number. A single 32-bit number can represent 4,294,967,295 unique numbers which definitely sounds like a lot, but as of 2017, there are an estimated 7.5 billion humans on earth.
This means that the IPv4 standard doesn’t even have enough IP addresses available for every person on the planet. It also can account for entire data centers filled with thousands and thousands of computers required for large scale technology companies to operate.
So, in 1996, RFC 1918 was published. RFC stands for Request for Comments and has a long-standing way for those responsible for keeping the internet running to agree upon the standard requirements to do so.
RFC 1918, outlined a number of networks that would be defined as non-routable address space. Non-routable address space is basically exactly what it sounds like.
They are ranges of IPs set aside for use by anyone that cannot be routed to. Not every computer connected to the internet needs to be able to communicate with every other computer connected to the internet.
Non-routable address space allows for nodes on such a network to communicate with each other but no gateway router will attempt to forward traffic to this type of network.
RFC 1918 defined three ranges of IP addresses that will never be routed anywhere by core routers. That means that they belong to no one and that anyone can use them. In fact, since they are separated from the way traffic moves across the internet, there’s no limit to how many people might use these addresses for their internal networks.
The primary three ranges of non-routable address space
- 10.0.0.0/8
- 172.16.0.0/12
- 192.168.0.0/16
These ranges are free for anyone to use for their internal networks. It should be called out that interior gateway protocols will route these address spaces. So, they are appropriate for use within an autonomous system but exterior gateway protocols will not.