User:AbdoHelaly

IPv4 Subnet Equation By Abdelrahman Mohamed

How to calculate IP address subnet information (Network, Broadcast, First IP, Last IP)?

It's too simple equation to calculate IPv4 Subnet Network ID.

* Used and Tested with Class C Subnets.

First Of All ,, Keep this Subnet Hosts Map in mind (Number of Hosts per Prefix):

Using Equation:

Network ID: floor(Host Address/Subnet Number of Hosts) * Subnet Number of Hosts

Broadcast ID: (Host ID + (Subnet Number of Hosts-1))

First Host: Network ID + 1

Last Host: Broadcast ID - 1

Ex1: 192.168.1.65/28: 65/16 = 4.0625       Network ID: 4*16 = 64           (192.168.1.64) Broadcast ID: 64+(16-1) = 79   (192.168.1.79) First Host ID: 64 + 1 = 65     (192.168.1.65) Last Host ID: 79 - 1 = 78      (192.168.1.78)

Ex2: 192.168.20.166/25: 166/128 = 1.296875       Network ID: 1*128 = 128         (192.168.20.128) Broadcast ID: 128+(128-1) = 255 (192.168.20.255) First Host ID: 128 + 1 = 129   (192.168.20.129) Last Host ID: 255 - 1 = 254    (192.168.20.254)

Ex3: 192.168.30.14/29: 14/8 = 1.75       Network ID: 1*8 = 8             (192.168.30.8) Broadcast ID: 8+(8-1) = 15     (192.168.30.15) First Host ID: 8 + 1 = 9       (192.168.30.9) Last Host ID: 15 - 1 = 14      (192.168.30.14)

Ex4: 192.168.20.86/30: 86/4 = 21.5       Network ID: 21*4 = 84           (192.168.20.84) Broadcast ID: 84+(4-1) = 87    (192.168.20.87) First Host ID: 84 + 1 = 85     (192.168.20.85) Last Host ID: 87 - 1 = 86      (192.168.20.86)