Table 259 Subnet 1; Table 260 Subnet 2 - ZyXEL Communications Internet Security Appliance ZyWALL5UTM 4.0 User Manual

ZyWALL 5/35/70 Series User's Guide
Note: In the following charts, shaded/bolded last octet bit values indicate host ID bits
"borrowed" to form 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 259 Subnet 1

IP Address
IP Address (Binary)
Subnet Mask
Subnet Mask (Binary)
Subnet Address: 192.168.1.0
Broadcast Address:
192.168.1.127

Table 260 Subnet 2

IP Address
IP Address (Binary)
Subnet Mask
Subnet Mask (Binary)
Subnet Address:
192.168.1.128
Broadcast Address:
192.168.1.255
The remaining 7 bits determine the number of hosts each subnet can have. Host IDs of all
zeros represent the subnet itself and host IDs of all ones are the broadcast address for that
subnet, so the actual number of hosts available on each subnet in the example above is 2
or 126 hosts for each subnet.
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.
693
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.
Lowest Host ID: 192.168.1.129
Highest Host ID: 192.168.1.254
LAST OCTET BIT
VALUE
0
00000000
128
10000000
LAST OCTET BIT VALUE
128
10000000
128
10000000
7
Appendix E IP Subnetting
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