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It is small question, but I can't figure out these things. Please help me in simply way how to do this.

Consider the given ip address is 198.51.100.39/28. From this how can I found the first ,last and the number of address in this network

Esa Jokinen
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Bewani Anuththara
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    See [How do you calculate the prefix, network, subnet, and host numbers?](https://networkengineering.stackexchange.com/q/7106/8499). It is simple binary math. – Ron Maupin Jun 23 '18 at 10:07
  • If you have a linux machine - install ipcalc $ ipcalc 198.51.100.39/28 Address: 198.51.100.39 11000110.00110011.01100100.0010 0111 Netmask: 255.255.255.240 = 28 11111111.11111111.11111111.1111 0000 Wildcard: 0.0.0.15 00000000.00000000.00000000.0000 1111 => Network: 198.51.100.32/28 11000110.00110011.01100100.0010 0000 HostMin: 198.51.100.33 11000110.00110011.01100100.0010 0001 HostMax: 198.51.100.46 11000110.00110011.01100100.0010 1110 Broadcast: 198.51.100.47 11000110.00110011.01100100.0010 1111 – Keiran Holloway Jun 23 '18 at 10:47

1 Answers1

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The math behind requires converting IPv4 notation and CIDR block into binary.

198.51.100.39    in binary  11000110 00110011 01100100 00100111
255.255.255.240  (for /28)  11111111 11111111 11111111 11110000
---------------------------------------------------------------
FIRST (from logical AND)    11000110 00110011 01100100 00100000
LAST  (host bits => 1)      11000110 00110011 01100100 00101111

These converted back into IPv4 notation gives range 198.51.100.32 - 198.51.100.47.

The number of addresses can be calculated directly from CIDR (/28): 2³²⁻²⁸ = 2⁴ = 16.

If you don't want to do this every time, you can use a CIDR to IPv4 Conversion tool.

Esa Jokinen
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