ZyXEL Communications wap3205 V3 User Manual page 90

As these two IP addresses cannot be used for individual hosts, calculate the maximum number of
possible hosts in a network as follows:
Table 39 Maximum Host Numbers
SUBNET MASK
8 bits 255.0.0.0
16 bits 255.255.0.0
24 bits 255.255.255.0
29 bits 255.255.255.248
Notation
Since the mask is always a continuous number of ones beginning from the left, followed by a continuous
number of zeros for the remainder of the 32 bit mask, you can simply specify the number of ones instead
of writing the value of each octet. This is usually specified by writing a "/" followed by the number of bits
in the mask after the address.
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.
Table 40 Alternative Subnet Mask Notation
SUBNET MASK
255.255.255.0
255.255.255.128
255.255.255.192
255.255.255.224
255.255.255.240
255.255.255.248
255.255.255.252
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
2 or 254 possible hosts.
The following figure shows the company network before subnetting.
Appendix A IP Addresses and Subnetting
HOST ID SIZE
24 bits
16 bits
8 bits
3 bits
ALTERNATIVE LAST OCTET
NOTATION (BINARY)
/24 0000 0000
/25 1000 0000
/26 1100 0000
/27 1110 0000
/28 1111 0000
/29 1111 1000
/30 1111 1100
WAP3205 v3 User's Guide
90
MAXIMUM NUMBER OF HOSTS
24
2 – 2 16777214
16
2 – 2 65534
8
2 – 2 254
3
2 – 2 6
LAST OCTET
(DECIMAL)
0
128
192
224
240
248
252
8
–