TCP/IP Made Easy
 

Class A:  1 - 126  (127 is used for localhost, or self test)
Class B:  128 - 191 (Stops before the most commonly used one- 192)
Class C:  192 - 223

Class A uses one subnet masking (255.0.0.0)
Class B uses two subnet masking (255.255.0.0)
Class C uses three subnet masks (255.255.255.0)

TCP/IP is today's most popular network protocol and is the protocol in the Internet. It is a routable protocol that provides connection between heterogeneous systems, these are the main reasons the protocol is so widely adapted; for example it allows communication between UNIX, Windows, Netware and Mac OS computers spread over multiple interconnected networks. The "TCP/IP protocol" is actually the "TCP/IP suite" composed of many different protocols each with its own functions. The two main protocols are in its name: the Internet Protocol and the Transmission Control Protocol.

IP addressing is assigning a 32-bit logical numeric address to a network device. Every IP address on the network must be unique. An IP address is represented in a dotted decimal format, for example: 159.101.6.8. As you can see the address is divided in 4 parts, these parts are called octets. The current used addressing schema in version 4 of IP is divided in 5 Classes:
Classes     First Octet
Class A     1-126 (127 is local host)
Class B     128-191
Class C     192-223
Class D     224-239
Class E     240-254

A subnet mask is used to determine which part is the network part and which is the host part.
Default subnet masks:
Class A     255.0.0.0
Class B     255.255.0.0
Class C     255.255.255.0

IANA reserved 4 address ranges to be used in private networks, these addresses won't appear on the Internet avoiding IP address conflicts:
- 10.0.0.0 through 10.255.255.255
- 172.16.0.0 through 172.31.255.255
- 192.168.0.0 through 192.168.255.255
- 169.254.0.1 through 169.254.255.254 (reserved for Automatic Private IP Addressing)

How did we get those numbers?

• Remember we use DIGITS (10 fingers or 10 digits), or to the power of 10.
• Computers use Binary. 1 and 0, or ON/OFF, True/False, Positive/Negative, or to the power of 2.
• Anything to the power of "0" is one (1), no matter who - 10¹, 16¹, 2¹ all equal 1.

1.  Start by putting 8 hash marks across your page.

2.  Put the digital equivalents above the marks. (Left  side is called High Order) and use the lower part to "turn on or off" the bits.  Meaning 10101010 would equal 170

So to get #192 in binary, you would add 128+64 which would equal 192. Turn on the bits to show this:  11000000.

What about #240?  Ok, 128+64+32+16=240 or shown as 11110000
Same with say #25.  16+8+1=25 would show as 00011001. 
Don't be fooled on tests, they will leave out the first 0's.  There always has to be 8 digits.
Likewise, 1111111 would be #127 right? There is always a " 0" in front of the numbers.

3.  What about subnet masks. - thanks to Dan at Infogem on simplifying masking.
Not to confused with CIDR, but if you are given 192.168.105.12/27 then that would mean you hold back 25 bits, and use what is left over.

4.  Going to our above chart, replace the power row by adding the number previous to it:
For example, 128+64= 192; 192+32=224; 224+16=240  and so on.

Now count back the reserved bits, in this case the /27.  Remember there are 3 other sets of bits ahead of this, meaning 8x3=24, so we have 3 left to grab.  The subnet mask will be the number to the right of it.

So our mask would be 255.255.255.240.  Mask is always to the right of your last hold back bit.

Try another... 192.168.105.24/28

So our mask would be 255.255.255.248.  Simple eh!

CIDR

Classless Internet Domain Registry (Registration) follows the same idea, but tells you how many computers you are restricted to use by Internic.

You might buy an IP address like 200.46.2.3 but it will have a conditional "slash" on the end. To use our example, 20.46.2.3/28 will be the number you buy instead of a full Class A.

So using the above chart, hold back the amount of bits INTERNIC tells you to, in this case 28. Think of a loaf of bread.  We have 32 slices in this loaf.  But there isn't enough bread to go around, so we have to cut back on them, INTERNIC keeps 28 slices, you have 4 left to use. Or the total 32 - 28 = 4.

Now take the remainder and convert that to decimal.  Here we have 4 left, so I I I I is:
8+4+2+1= 15.  You can use 15 IP addresses only, instead of the 255 normally allocated.

IPV6

IPv6 (version 6) will be 128 bit and will use 8 sets of number and use Hexadecimal to look like some horrible number like:

 3ffe:8114::1 - where the :: represents 0 or where an old IP4 router can understand it or what I remember seeing: 3F56.34DF.AAB5.CF34:

IPv6 supports addresses which are four times the number of bits as IPv4 addresses (128 vs. 32). This is 4 Billion times 4 Billion times 4 Billion (2^^96) times the size of the IPv4 address space (2^^32). This works out to be:

340,282,366,920,938,463,463,374,607,431,768,211,456

This is an extremely large address space. In a theoretical sense this is approximately 665,570,793,348,866,943,898,599 addresses per square meter of the surface of the planet Earth (assuming the earth surface is 511,263,971,197,990 square meters).

Or to bring it closer to home.  Every man, woman, and child, and yes pets, can have their own IP address or new Social Security/Insurance Number.  Use this number in an RFID (radio frequency ID) implant and presto! Talk about Minority Report - anyone in charge can know where you are at in the world.

What about Hexadecimal?

Simply put, it is base 16, meaning everything is done in 16's. now.   For BUL (Big Ugly Number) use your Calculator to figure it out, I'm not going to do all you work for you!  Start/Run, type "calc", make sure VIEW is on Scientific, click on the radio button that says DEC; then type in the number, click on HEX button.  You can do that for BIN binary to decimal and so on.

We use Digital 0-9 (10 numbers) while Hex takes us further, A=10, all the way to F=15 to give us 16 numbers. 

Easiest is to just use the last 4 columns.  Meaning if I have "3F8" (memory address for Com1) then it would be the same as 3x256 + 15x16 + 8x1 = 1016

Hope this helps.

Cheers
Tom.