Local IP

[Adaz]

Does someone know, why "192.168" is the beginning of the local IP address?
Who and when decided to use this?

[ale870]

Hi,

that one is the default ip address used by windows in order to create/configure a local (home)  network.

Example, if you have 3 PC, and you use a router to go to internet, probably you will have: 192.168.0.1, 192.168.0.2, 192.168.0.3.

[Adaz]

Absolutely not :)

192.168 is not the windows default ip, that is 169.254.x.x
192.168 is a manual address you set in your router or computer for local communication.

My question is: why exactly 192.168.x.x?

[ale870]

Usually routers use such IP address, since that one belongs to a private IP class (you cannot find such IP class over internet).

It means evey local PC connected to the router will follow that pattern.

(usually it uses a mask like 255.255.0.0 or 255.255.255.0).

[ale870]

Take a look to this article:

http://technet2.microsoft.com/WindowsServer/en/library/22aa0206-2cbd-4c79-bedd-8e52b93159931033.mspx?mfr=true

[Adaz]

Take a look to this article:
http://technet2.microsoft.com/WindowsServer/en/library/22aa0206-2cbd-4c79-bedd-8e52b93159931033.mspx?mfr=true

That's not an answer for my question, and was not a denial of my statement.

[Adaz]

Usually routers use such IP address, since that one belongs to a private IP class (you cannot find such IP class over internet).

Yes, yes, yes, I know! But why "192.168", I cannot explain with other words...

[ale870]

The "secret" is inside IP classes.

Briefly, a network is divided in 3 classes: A, B, C.

You can detect which class type you are using analyzing your IP address.

For every class, there are some "special" IP reserved to "not connected networks". What are "not connected networks"?
They are the networks that use an IP address but they are NOT connected to Internet.

These are the addresses:

Class A (one network):
10.0.0.0

Class B (16 networks):
172.16.0.0 -> 172.31.0.0

Class C (256 networks):
192.168.0.0 -> 192.168.255.0

It means if you want to create a private network (tipically network created inside an office, or inside your home) you should have to use such network addresses.

[Adaz]

Thank you, but I repeat: I already knew it!

My question again, with other words:

Why 10.x.x.x, why not e.g. 11.x.x.x

Why 172.16.x.x -> 172.31.x.x, why not 173.15.x.x

Why 192.168.x.x -> 192.168.255.x, why not 100.100.x.x, or 200.200.x.x, etc.


Do you begin to understand my question?

[ale870]

There is a consortium which established these information.
When you want to put a computer in internet as provider, since you need a public static address, (e.g.: google), you need to get an ip address, which is supplied by ICANN (http://www.icann.org) and IANA (http://www.iana.org).

Since public internet addresses are very limited, ICANN has "the list" of IP still available.

Generally speaking, people established some guidelines to help electronic instruments, government, associations, etc... to understand which addresses should be used and how.

The classes (A, B, C) come from an easy calculation:

e.g.: class "A" uses the most left 8 digits to identify the network, but the most left digit is always set to "0"; then eliminate "127.0.0.1" (loop back) and "0.0.0.0" (default route) so you will get: class A.

For other classes is the same.

ICANN & IANA supplyed official directives.

[Adaz]

Ok, for me it's more clear now :)
So probably the binary "look" of the numbers is the reason for the decimal numbers. E.g.:
192 = 11000000
168 = 10101000
127 = 01111111

But 10101010 would be nicer :-)  (it's 170) So why 168, and not 170? :))

Be that as it may, never mind, thank you for your reply!

[ale870]

But 10101010 would be nicer :-)  (it's 170) So why 168, and not 170?

Did you see to the ICANN/IANA sites if there is an answer?

Sometimes the decisions are made considering security reasons, or checksum reasons (to verify if the transmission was correctly made), etc...

I will ask it to some specialists that I know (just for curiosity).

Bye!

[Adaz]

Ok, I would be thankful :)