ZyXEL Communications VFG6005, User Manual

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For example, 192.1.1.0 /25 is equivalent to saying 192.1.1.0 with subnet mask 255.255.255.128.
The following table shows some possible subnet masks using both notations.
Alternative Subnet Mask Notation
SUBNET
MASK
ALTERNATIV
E NOTATION
LAST OCTET
(BINARY)
LAST OCTET
(DECIMAL)
255.255.255.0 /24 0000 0000 0
255.255.255.128 /25 1000 0000 128
255.255.255.192 /26 1100 0000 192
255.255.255.224 /27 1110 0000 224
255.255.255.240 /28 1111 0000 240
255.255.255.248 /29 1111 1000 248
255.255.255.252 /30 1111 1100 252
Subnetting
You can use subnetting to divide one network into multiple sub-networks. In the following example a network administrator
creates two sub-networks to isolate a group of servers from the rest of the company network for security reasons.
In this example, the company network address is 192.168.1.0. The first three octets of the address (192.168.1) are the
network number, and the remaining octet is the host ID, allowing a maximum of 2
8
– 2 or 254 possible hosts.
The following figure shows the company network before subnetting.