Concept derived from Udemy class - introduction to subnetting
How to do subnetting
- Understanding subnetting basic
- IPv4 addressing
- Numbering systems
Before Subneting
IP Address
- Network Identifier
- Host Identifier
After subnetting
IP address
- Network Identifier
- Host Identifier
- Subnet Identifier
- Host Identifier
Binary basic
Numbering system
- Decimal
- Binary (Base2)
- Base10
1. Decimal numbers include
- 0 to 9
- Noted as Decimal or Dec
Decimal numbers
1 to any number does not matter
0, 5 10, 12345 999934343434
All numbers are decimal numbers.
Binary numbers
- Binary number include
-> 1 and 0
- Binary numbers are always 1 and 0
For example
0, 1, 10, 110, 110011 ......
Please note: 1 in binary does not mean 1 in decimal.
- Every binary number has a corresponding decimal value and vice-versa.
Binary number Decimal Equivalent
------------ ------------------
1 1
10 2
1010 10
1111 15
Converting from binary to decimal
Each position for a binary number has a value
There are 8 positions and from right to left the power of 2 to 0 to 7
so we have
- - - - - - - -
2^7 2^6 2^5 2^4 2^3 2^2 2^1 2^0
128 64 32 16 8 4 2 1
Now, start from right to convert 1010
It takes 4 positions from right side
1 0 1 0
--- -- -- -- -- -- -- --
128 64 32 16 8 4 2 1
---------------------------------------------------------
8 0 2 0
so we add which position value is 1, not the 0.
so, we have 8+0+0+2 = 10
1010 in binary is equal to 10 in decimal.
Note: If you have more binary number, you keep adding 2^x.
so you will have 2^8, 2^9 and so on.
Terminology
-----------
Bits
Bytes
Octets
Bits
- Smallest number you can represent
- In binary bits are 1s and 0s.
- Bits are infact electrical signals such as on or off.
Bytes
- Bytes are group of 8 bits. 11111111
Octets
- Octets are grouping of 8 bits.
- For eg, 11111111.11111111.00000000.00000000 (NetMask)
How many different numbers?
- Lets tryUsing 2 bits (2^2 =4)
- There are 4 different binary numbers with two bits.
-> 00 (i.e. decimal 0)
-> 01 (i.e. decimal 1)
-> 10 (i.e. decimal 2)
-> 11 (i.e. decimal 3)
So, we have combinaton of 1s and 0s produces 4 different binary number.
-> Now try with 3 bits (2^3 - two to the power 3 = 8)
2^4 = 16 bits
-> There are eight different binary numbers with three bits:
-> 000 (i.e. decimal 0)
-> 001 (i.e. decimal 1)
-> 010 (i.e. decimal 2)
-> 011 (i.e. decimal 3)
-> 100 (i.e. decimal 4)
-> 101 (i.e. decimal 5)
-> 110 (i.e. decimal 6)
-> 111 (i.e. decimal 7)
Now, converting from Decimal to a Binary
----------------------------------------
Now, take the decimal number and use the substraction. Lets pick a number 185
can we substract 185 from 128? lets try
185
-128
----
057
now, the next number is 64, can we substract 64, no, so we use 0,
next number is 32, can we substract, yes, so
57
-32
---
25
now, next number is 16, can we substract, yes
25-16=9
how about 8, yes we can
9-8=1
now, can we substract 1 from 1, yes
1-1=0
so we have
so, we can simplyfy this way, whereever you can substract, you use 1 and wherever you can't
use 0, so you get the answer
1 0 1 1 1 0 0 1
--- --- --- --- --- --- --- ---
128 64 32 16 8 4 2 1
Decimal number 185, can you substract 128 from 185? Yes
--- --- --- --- --- --- --- ---
128 64 32 16 8 4 2 1
so, the binary number of 185 is = 10111001
if you want to convert do dec, do the math
128 64 32 16 8 4 2 1
--- --- --- --- --- --- --- ---
1 0 1 1 1 0 0 1
----------------------------------------------------------
128 + 0 + 32 + 16 + 8 + 0 + 0 + 1
128+32+16+8+1=185
Note: Subnet is build on binary system
1 0 0 1 0 1
128 64 32 16 8 4 2 1
---------------------------------------------------------
32+4+1=37
1. 10101010=128+42= 170
2. 10001101=141
3. 10010111=151
4. 01010101=85
5. 100101=37
6. 01111101
125-64= 61-32=29-16=13-8=5-4=1-1=0 [128 is missing so we add 0]
01111101
7. 63=00111111
63-32=31-16=15-8=7-4=3-2=1-1=0 [Missing values are 0, since we are missing for 128 and 64]
8. 48=110000 => 00110000
48-32=16-16=0
9. 250 = how?
11111010
10. 3608= 111000011000 how?
-----------------------------------------------
Numbering systems - Binary math
In binary, everything is 1s and 0s.
Binary addition
Note: in binary 1+1 is not equal to 2. It is either 0 or 1.
Lets add
1 1 1
+ 1
-----------------
we add from right side 1+1, so value does not fit or we can't do it, we add 0
and 1 goes to 2s position
so it becames like this
1 1 1
+ 1
-----------------
0 0
same thing happens and the 1 moves to 3rd position
1 1 1
+ 1
-----------------
0 0 0
again 0, so I moves to new position - 4th
so we add 0 to 4th position and add 1
so, the result is 0+1=1
0 1 1 1
+ 1
--------------------------
1 0 0 0
Now, lets convert this binary number into decimal
0 0 0 0 1 0 0 0
--- --- --- --- --- --- --- ---
128 64 32 16 8 4 2 1
2^7 2^6 2^5 2^4 2^3 2^3 2^1 2^0
------------------------------------------------------------
0 + 0 + 0 + 0 + 8 + 0 + 0 + 0
--------------------------------------------------------
=8
NOW, lets add another value
1 0 1
+ 1
--------------------------
0
here, 1+1=0, because we can't add there,
next step
1 0 1
+ 1 1
--------------------------
1 0
0+1=1, here we can add 0 and 1 which becomes 1
so, we have no more value to add, so the final result is
1 0 1
+ 1 1
--------------------------
1 1 0
110
convert this binary number to decimal
we have only 3 numbers, we its
1 1 0
2^2 + 2^1 + 2^0
4 + 2 + 1
---------------------
4 + 2 + 0 =6
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