ZyXEL Communications 2WE Example: Four Subnets, Chart K-7Subnet, Chart K-8Subnet

ZyWALL 2 and ZyWALL 2WE

192.168.1.0 with mask 255.255.255.128 is the subnet itself, and 192.168.1.127 with 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 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 26-2 or 62 hosts for each subnet (all 0’s is the subnet itself, all 1’s is the broadcast address on the subnet).

Chart K-7 Subnet 1

	NETWORK NUMBER				LAST OCTET BIT VALUE
IP Address	192.168.1.		0
IP Address (Binary)	11000000.10101000.00000001.						000000
					00
Subnet Mask (Binary)	11111111.11111111.11111111.						000000
					11
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 K-8 Subnet 2
	NETWORK NUMBER				LAST OCTET BIT VALUE
IP Address	192.168.1.		64
IP Address (Binary)	11000000.10101000.00000001.					000000
				01
Subnet Mask (Binary)	11111111.11111111.11111111.					000000
				11
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

IP Subnetting 49