# Class D subnets

I have seen online , where they mention Class D:
CIDR block 224.0.0.0/4
Range: Network - Broadcast  224.0.0.0 - 239.255.255.255

I am not sure why it goes from 224 to 239. How did they come up with it ? since it is /4 as notation?

they even say Netmask = 240.0.0.0

Confusing to me

Thank you
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Author Commented:
it says  class D uses first 4 bits 1110...  which means 224 and 1111 is 240
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Fixer of ProblemsCommented:
That's what my links say also.
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Commented:
IP is a binary notation where the first 4-bits of the first octet decides which class the IP address will fall into.

Here is the rule

Class A - First octet has to be between 0000 0000 - 0111 1111 - in decimal 0 - 127 ( 127 is reserved for loopback)
Class B - First octet has to be between 1000 0000 - 1011 1111 - in decimal 128 - 191
Class C - First octet has to be between 1100 0000 - 1101 1111 - in decimal 192 - 223
Class D - First octet has to be between 1110 0000 - 1110 1111 - in decimal 224 - 239
Class E - First octet has to be between 1111 0000 - 1111 1111 - in decimal 240 - 255

Class D will be the IP addresses where the first bit is between 1110 0000 - 1110 1111 that is 224 - 239.
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Author Commented:
Thank you Guys
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