ZyXEL MI-7248 User Guide - Page 282

Example: Two Subnets

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Appendix A IP Addresses and Subnetting 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 119 Two Subnets Example IP/SUBNET MASK NETWORK NUMBER HOST ID IP Address 192.168.1. 0 IP Address (Binary) 11000000.10101000.00000001. 00000000 Subnet Mask 255.255.255. 0 Subnet Mask (Binary) 11111111.11111111.11111111. 00000000 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. " 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 120 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 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 LAST OCTET BIT VALUE 0 00000000 128 10000000 Table 121 Subnet 2 IP/SUBNET MASK IP Address IP Address (Binary) Subnet Mask Subnet Mask (Binary) NETWORK NUMBER 192.168.1. 11000000.10101000.00000001. 255.255.255. 11111111.11111111.11111111. LAST OCTET BIT VALUE 128 10000000 128 10000000 282 MS-7206 User's Guide

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Appendix A IP Addresses and Subnetting
MS-7206 User’s Guide
282
Example: Two Subnets
As an example, you have a class “C” address 192.168.1.0 with subnet mask of 255.255.255.0.
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.
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 119
Two Subnets Example
IP/SUBNET MASK
NETWORK NUMBER
HOST ID
IP Address
192.168.1.
0
IP Address (Binary)
11000000.10101000.00000001.
00000000
Subnet Mask
255.255.255.
0
Subnet Mask (Binary)
11111111.11111111.11111111.
00000000
Table 120
Subnet 1
IP/SUBNET MASK
NETWORK NUMBER
LAST OCTET BIT
VALUE
IP Address
192.168.1.
0
IP Address (Binary)
11000000.10101000.00000001.
0
0000000
Subnet Mask
255.255.255.
128
Subnet Mask (Binary)
11111111.11111111.11111111.
1
0000000
Subnet Address: 192.168.1.0
Lowest Host ID: 192.168.1.1
Broadcast Address:
192.168.1.127
Highest Host ID: 192.168.1.126
Table 121
Subnet 2
IP/SUBNET MASK
NETWORK NUMBER
LAST OCTET BIT VALUE
IP Address
192.168.1.
128
IP Address (Binary)
11000000.10101000.00000001.
1
0000000
Subnet Mask
255.255.255.
128
Subnet Mask (Binary)
11111111.11111111.11111111.
1
0000000