CIDR = Classless Inter - Domain Routing
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Class A = 10.1.1.10
subnet mask = 255.0.0.0
11111111.00000000.00000000.00000000
CIDR ==> 10.1.1.10 / 8
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Class B = 172.16.30.31
subnet mask = 255.255.0.0
11111111.11111111.00000000.00000000
CIDR ==> 172.16.30.31 / 16
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Class C = 192.168.100.1
subnet mask = 255.255.255.0
11111111.11111111.11111111.00000000
CIDR ==> 192.168.100.1 / 24
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CIDR -> 10.1.10.100 / 10
subnet -> 11111111.11000000.00000000.00000000
255 . 192 . 0 . 0
CIDR -> 172.16.30.31 / 21
subnet-> 11111111.11111111.11111000.00000000
255 . 255 . 248 . 0
CIDR -> 192.168.100.1 / 31
subnet-> 11111111.111111111.111111111.1111111110
255 . 255 . 255 . 254
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