Subnetting

l0ll000l = 128+32+16+1

=177

​Example

Each Bit of a binary octet has a value

l l l l l l l l

128,64,32,16,8,4,2,1

So based on which bits are turned on will determine the decimal outcome.

To convert to to decimal to binary all you do is what you did but in reverse. So by using the numerical value of each bit to add up to the number you are trying to convert from.

​Example

​What is 152 in binary

128+16+8=152

=1001 1000

1010 0111= 1010 | 0111

A 7

So 1010 0001 in hex would be A7

​Example

When converting to hex from binary you want to split the octet into two parts. Once split each part represents a different value going through 1-9,A-F.

A=10 B=11 C=12 D=13 E=14 F=15

192.168.20.1/28= 255.255.255.1111 0000

2^4-2 = 16-2=14

There are 14 usable host bits

​Example

To identify the host bits of a subnet mask you first need to convert it into binary. Once converted to binary you need to count the 0's in the mask. Once you figure that out you use the formula 2^x - 2

What class is this IP: 192.168.17.32

The first octet of the IP address is 192 so the IP address 192.168.17.32

is a Class C address

Example

A IP address can be apart of 3 different classes: Class A(1-126), Class B(128-191), Class C(192-223) based on the first octet of the IP. Depending on the class of the address will determine which octets are host and network.

Is 192.168.6.0 a valid IP address.

192.168.6|0

192.168.6|0000 0000

No its not a valid IP address because the host section is all 0's

Example

​When identifying weather a IP address is valid for you need to identify what class the IP address is apart of.

A IP address can be apart of 3 different classes: Class A(1-126), Class B(128-191), Class C(192-223) based on the first octet of the IP. Depending on the class of the address will determine which octets are host and network. Class A(1|1.1.1), Class B(128.1|1.1), Class C(192.1.1|1). It will only be valid if the host or network part is not all 0's or all 1's.