
Ask HN: What does each part of an IP Address represent? - thisismyhnuser
What does each component of an IP Address represent? Take &quot;215.54.87.2&quot;. According to https:&#x2F;&#x2F;www.iplocation.net&#x2F; this IP address is located in Columbus, Ohio. (I made up those numbers....it is just some random Jerry.)<p>Does &quot;215.&quot; essentially say the IP address is located in the US, &quot;215.54.&quot; say it is in Ohio and &quot;215.54.87.&quot; say it is a company in Columbus? Further, a single company would own the block of &quot;215.54.87.*&quot;, 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&#x27;t seem to find a good tutorial on IP addresses for dummies.
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detaro
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.

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).

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.

I hope that is somewhat understandable, I'm having a hard time putting it in
words...

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.

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Spoom
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>).

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].

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.

0\.
[https://www.arin.net/fees/fee_schedule.html](https://www.arin.net/fees/fee_schedule.html)

1\.
[https://www.arin.net/resources/request/ipv4_countdown.html](https://www.arin.net/resources/request/ipv4_countdown.html)

2\. [https://xkcd.com/195/](https://xkcd.com/195/)

~~~
thisismyhnuser
I can't even read the arin.net pages...does something screwy to my
browser...both Chrome and Firefox in Linux.

~~~
herbst
Works for me on chrome on ubuntu.

