ZyXEL Communications Internet Security Gateway ZyWALL 2 Series - Manual (Page 565)

ZyWALL 2 Series User’s Guide
IP Subnetting I-5
actual host for the first subnet is 192.168.1.1 and the highest is 192.168.1.126. Similarly the host ID range for
the second subnet is 192.168.1.129 to 192.168.1.254.
Example: Four Subnets
The above example illustrated using a 25-bit subnet mask to divide a class “C” address space into two
subnets. Similarly to divide a class “C” address into four subnets, you need to “borrow” two host ID bits to
give four possible combinations of 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
2
6 -2 or 62 hosts for each subnet (all 0’s is the subnet itself, all 1’s is the broadcast address on the subnet).
Chart I-7 Subnet 1
NETWORK NUMBER LAST OCTET BIT VALUE
IP Address 192.168.1. 0
IP Address (Binary) 11000000.10101000.00000001. 00000000
Subnet Mask (Binary) 11111111.11111111.11111111. 11000000
Subnet Address: 192.168.1.0 Lowest Host ID: 192.168.1.1
Broadcast Address: 192.168.1.63 Highest Host ID: 192.168.1.62
Chart I-8 Subnet 2
NETWORK NUMBER LAST OCTET BIT VALUE
IP Address 192.168.1. 64
IP Address (Binary) 11000000.10101000.00000001. 01000000
Subnet Mask (Binary) 11111111.11111111.11111111. 11000000
Subnet Address: 192.168.1.64 Lowest Host ID: 192.168.1.65
Broadcast Address: 192.168.1.127 Highest Host ID: 192.168.1.126
Chart I-9 Subnet 3
NETWORK NUMBER LAST OCTET BIT VALUE
IP Address 192.168.1. 128
IP Address (Binary) 11000000.10101000.00000001. 10000000
Subnet Mask (Binary) 11111111.11111111.11111111. 11000000
Subnet Address: 192.168.1.128 Lowest Host ID: 192.168.1.129
Broadcast Address: 192.168.1.191 Highest Host ID: 192.168.1.190