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):

Network Prefix	Number of IPs
24	256 IPs
25	128 IPs
26	64 IPs
27	32 IPs
28	16 IPs
29	8 IPs
30	4 IPs

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)