ZyXEL P-660HW-T1 v3 User Guide - Page 390

Example: Four Subnets

Page 390 highlights

Appendix C IP Addresses and Subnetting In a 25-bit subnet the host ID has 7 bits, so each sub-network has a maximum of 27 - 2 or 126 possible hosts (a host ID of all zeroes is the subnet's address itself, all ones is the subnet's broadcast address). 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 124 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 LAST OCTET BIT VALUE 0 00000000 11000000 Highest Host ID: 192.168.1.62 Table 125 Subnet 2 IP/SUBNET MASK IP Address IP Address (Binary) Subnet Mask (Binary) Subnet Address: 192.168.1.64 Broadcast Address: 192.168.1.127 NETWORK NUMBER LAST OCTET BIT VALUE 192.168.1. 64 11000000.10101000.00000001. 01000000 11111111.11111111.11111111. 11000000 Lowest Host ID: 192.168.1.65 Highest Host ID: 192.168.1.126 390 P-660HW-Tx v3 Series User's Guide

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Appendix C IP Addresses and Subnetting
P-660HW-Tx v3 Series User’s Guide
390
In a 25-bit subnet the host ID has 7 bits, so each sub-network has a maximum of
2
7
– 2 or 126 possible hosts (a host ID of all zeroes is the subnet’s address itself,
all ones is the subnet’s broadcast address).
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.
11
000000) or 255.255.255.192.
Each subnet contains 6 host ID bits, giving 2
6
- 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 124
Subnet 1
IP/SUBNET MASK
NETWORK NUMBER
LAST OCTET BIT
VALUE
IP Address (Decimal)
192.168.1.
0
IP Address (Binary)
11000000.10101000.00000001.
00
000000
Subnet Mask (Binary)
11111111.11111111.11111111.
11
000000
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
Table 125
Subnet 2
IP/SUBNET MASK
NETWORK NUMBER
LAST OCTET BIT
VALUE
IP Address
192.168.1.
64
IP Address (Binary)
11000000.10101000.00000001.
01
000000
Subnet Mask (Binary)
11111111.11111111.11111111.
11
000000
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