ZyXEL Communications NBG-416N User Manual page 160

Appendix A IP Addresses and Subnetting
As these two IP addresses cannot be used for individual hosts, calculate the
maximum number of possible hosts in a network as follows:
Table 57 Maximum Host Numbers
SUBNET MASK
8 bits
16 bits 255.255.0.0
24 bits 255.255.255.0
29 bits 255.255.255.2
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 58 Alternative Subnet Mask Notation
SUBNET
MASK
255.255.255.0
255.255.255.12
8
255.255.255.19
2
255.255.255.22
4
255.255.255.24
0
255.255.255.24
8
255.255.255.25
2
160
HOST ID SIZE
255.0.0.0 24 bits
16 bits
8 bits
3 bits
48
ALTERNATIVE
NOTATION
/24
/25
/26
/27
/28
/29
/30
MAXIMUM NUMBER OF
HOSTS
24
2 – 2 16777214
16
2 – 2 65534
8
2 – 2 254
3
2 – 2 6
LAST OCTET LAST OCTET
(BINARY) (DECIMAL)
0000 0000 0
1000 0000 128
1100 0000 192
1110 0000 224
1111 0000 240
1111 1000 248
1111 1100 252
NBG-416N User's Guide