What does each component of an IP Address represent? Take "215.54.87.2". According to https://www.iplocation.net/ this IP address is located in Columbus, Ohio. (I made up those numbers....it is just some random Jerry.)<p>Does "215." essentially say the IP address is located in the US, "215.54." say it is in Ohio and "215.54.87." say it is a company in Columbus? Further, a single company would own the block of "215.54.87.*", no? And that company may or may not be an ISP, right?<p>The above is for an IPv4 address...how does the breakdown work for IPv6 addresses?<p>I feel like these are stupid beginner questions but I can't seem to find a good tutorial on IP addresses for dummies.
The dots are just for human readability, showing the address byte-by-byte, and don't have any "meaning" anymore. Geographic structure is also only accidental.<p>Subdivisions nowadays happen nearly everywhere and noted with a a slash and a number after the IP address (e.g. 215.54.87.0/24 is the network containing all addresses where the first 24 bits are the same as in 215.54.87.0, 215.54.87.0/28 would be all the addresses where the first 28 bits are the same etc).<p>The rules differ a bit between the regions, but if I remember correctly a /24 is the smallest that can be officially assigned to an entity and announced in the global routing tables. They are free to slice smaller inside their networks though, and e.g. give a customer a /28 or /30 to use.<p>I hope that is somewhat understandable, I'm having a hard time putting it in words...<p>EDIT: IPv6 is same principle (although the notation for the address itself is now different). One important size there is /64, which is the subnet size for which automatic address assignment works, and the default size for subnets containing end devices. If you get IPv6 internet, you get at least a /64 (although a /56 is recommended), so you don't need NAT because you have more than enough addresses for everything.
You used to be able to buy blocks of public addresses from ARIN (and I guess you still can[0] but only under special circumstances[1]) but the IPv4 public assignment table is essentially full. You could buy blocks in class A (i.e you would own X.<all>.<all>.<all>), class B (X.Y.<all>.<all>), or class C (X.Y.Z.<all>).<p>The class assignments themselves are now either a result of an RFP (for special class IP blocks like multicast) or historical significance (basically, who grabbed it when it was available). XKCD had a comic in 2006 mapping the IPv4 assignment table[2].<p>I don't know much about IPv6 other than that its address space is so large that you essentially don't need to use NAT anymore, so I doubt we'll ever deplete it.<p>0. <a href="https://www.arin.net/fees/fee_schedule.html" rel="nofollow">https://www.arin.net/fees/fee_schedule.html</a><p>1. <a href="https://www.arin.net/resources/request/ipv4_countdown.html" rel="nofollow">https://www.arin.net/resources/request/ipv4_countdown.html</a><p>2. <a href="https://xkcd.com/195/" rel="nofollow">https://xkcd.com/195/</a>