266 Appendix G IP subnettingNN47922-501192.168.1.0 with mask 255.255.255.128 is the subnet itself, and 192.168.1.127with mask 255.255.255.128 is the directed broadcast address for the first subnet.Therefore, the lowest IP address that can be assigned to an actual host for the firstsubnet is 192.168.1.1 and the highest is 192.168.1.126. Similarly the host IDrange for the second subnet is 192.168.1.129 to 192.168.1.254.Example: four subnetsThe above example illustrated using a 25-bit subnet mask to divide a class Caddress space into two subnets. Similarly to divide a class C address into foursubnets, you need to borrow two host ID bits to give four possible combinationsof 00, 01, 10 and 11. The subnet mask is 26 bits(11111111.11111111.11111111.11000000) or 255.255.255.192. Each subnetcontains 6 host ID bits, giving 26-2 or 62 hosts for each subnet (all 0s is the subnetitself, all 1s is the broadcast address on the subnet).Table 62 Subnet 1Network number Last octet bit valueIP Address 192.168.1. 0IP Address (Binary) 11000000.10101000.00000001. 00000000Subnet Mask (Binary) 11111111.11111111.11111111. 11000000Subnet Address: 192.168.1.0 Lowest Host ID: 192.168.1.1Broadcast Address: 192.168.1.63 Highest Host ID: 192.168.1.62Table 63 Subnet 2Network number Last octet bit valueIP Address 192.168.1. 64IP Address (Binary) 11000000.10101000.00000001. 01000000Subnet Mask (Binary) 11111111.11111111.11111111. 11000000Subnet Address: 192.168.1.64 Lowest Host ID: 192.168.1.65Broadcast Address:192.168.1.127Highest Host ID: 192.168.1.126
