ZyXEL NBG6615 User Guide - Page 143
Example: Four Subnets, possible combinations 00
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Appendix A IP Addresses and Subnetting 192.168.1.0 with mask 255.255.255.128 is subnet A itself, and 192.168.1.127 with mask 255.255.255.128 is its broadcast address. Therefore, the lowest IP address that can be assigned to an actual host for subnet A is 192.168.1.1 and the highest is 192.168.1.126. Similarly, the host ID range for subnet B is 192.168.1.129 to 192.168.1.254. Example: Four Subnets The previous example illustrated using a 25-bit subnet mask to divide a 24-bit address into two subnets. Similarly, to divide a 24-bit address into four subnets, you need to "borrow" two host ID bits to give four possible combinations (00, 01, 10 and 11). The subnet mask is 26 bits (11111111.11111111.11111111.11000000) or 255.255.255.192. Each subnet contains 6 host ID bits, giving 26 - 2 or 62 hosts for each subnet (a host ID of all zeroes is the subnet itself, all ones is the subnet's broadcast address). Table 54 Subnet 1 IP/SUBNET MASK IP Address (Decimal) IP Address (Binary) Subnet Mask (Binary) Subnet Address: 192.168.1.0 Broadcast Address: 192.168.1.63 NETWORK NUMBER 192.168.1. 11000000.10101000.00000001. 11111111.11111111.11111111. Lowest Host ID: 192.168.1.1 Highest Host ID: 192.168.1.62 LAST OCTET BIT VALUE 0 00000000 11000000 Table 55 Subnet 2 IP/SUBNET MASK NETWORK NUMBER IP Address IP Address (Binary) Subnet Mask (Binary) Subnet Address: 192.168.1.64 Broadcast Address: 192.168.1.127 192.168.1. 11000000.10101000.00000001. 11111111.11111111.11111111. Lowest Host ID: 192.168.1.65 Highest Host ID: 192.168.1.126 LAST OCTET BIT VALUE 64 01000000 11000000 Table 56 Subnet 3 IP/SUBNET MASK IP Address IP Address (Binary) Subnet Mask (Binary) Subnet Address: 192.168.1.128 Broadcast Address: 192.168.1.191 NETWORK NUMBER 192.168.1. 11000000.10101000.00000001. 11111111.11111111.11111111. Lowest Host ID: 192.168.1.129 Highest Host ID: 192.168.1.190 LAST OCTET BIT VALUE 128 10000000 11000000 Table 57 Subnet 4 IP/SUBNET MASK IP Address IP Address (Binary) NETWORK NUMBER 192.168.1. 11000000.10101000.00000001. LAST OCTET BIT VALUE 192 11000000 NBG6615's User's Guide 143