Default Subnet masks

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default subnet masks     

How many bits in a default subnet mask?

Well let's look at the main 3 which are,

Class A = 24 bits default address is

Class B = 16 bits default address is

Class C = 8 bits default address is

The table below show the default subnet mask and it's number in binary

Remember "1" are for the network and "0" is for the host

So a class A network has a default subnet mask of the binary number for that is 11111111000000000000000000000000

What I like to do is break that binary number up in to octets which stops it looking so intimidating.

11111111 00000000 00000000 00000000

Look at my table below which shows the default for class a, b, c network

Class A 24 bits 11111111000000000000000000000000
Class B 16 bits 11111111111111110000000000000000
Class C 8 bits 11111111111111111111111100000000


 IP Range Reminder

1-126 Class A Network
128-191 Class B Network
192-223 Class C Network


You will notice we have left the number 127out this is because it is reserved for the loopback test. This allows you to send & receive data from the same port so you can see it works


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