Example: Two Subnets; Table 134 Two Subnets Example; Table 135 Subnet 1; Table 136 Subnet 2 - ZyXEL Communications P-660HW-T - V2 User Manual

P-660HW-T v2 User's Guide

Example: Two Subnets

As an example, you have a class "C" address 192.168.1.0 with subnet mask of 255.255.255.0.

Table 134 Two Subnets Example

IP/SUBNET MASK
IP Address
IP Address (Binary)
Subnet Mask
Subnet Mask (Binary)
The first three octets of the address make up the network number (class "C").
To make two networks, divide the network 192.168.1.0 into two separate subnets by
converting one of the host ID bits of the IP address to a network number bit. The "borrowed"
host ID bit can be either "0" or "1" thus giving two subnets; 192.168.1.0 with mask
255.255.255.128 and 192.168.1.128 with mask 255.255.255.128.
Note: In the following charts, shaded/bolded last octet bit values indicate host ID bits
"borrowed" to make network ID bits. The number of "borrowed" host ID bits
determines the number of subnets you can have. The remaining number of
host ID bits (after "borrowing") determines the number of hosts you can have
on each subnet.

Table 135 Subnet 1

IP/SUBNET MASK
IP Address
IP Address (Binary)
Subnet Mask
Subnet Mask (Binary)
Subnet Address: 192.168.1.0
Broadcast Address:
192.168.1.127

Table 136 Subnet 2

IP/SUBNET MASK
IP Address
IP Address (Binary)
Subnet Mask
Subnet Mask (Binary)
300
NETWORK NUMBER
192.168.1.
11000000.10101000.00000001.
255.255.255.
11111111.11111111.11111111.
NETWORK NUMBER
192.168.1.
11000000.10101000.00000001.
255.255.255.
11111111.11111111.11111111.
Lowest Host ID: 192.168.1.1
Highest Host ID: 192.168.1.126
NETWORK NUMBER
192.168.1.
11000000.10101000.00000001.
255.255.255.
11111111.11111111.11111111.
HOST ID
0
00000000
0
00000000
LAST OCTET BIT
VALUE
0
00000000
128
10000000
LAST OCTET BIT VALUE
128
10000000
128
10000000
Appendix F IP Subnetting