Notation – ZyXEL Communications NBG-417N User Manual
Page 208
Appendix A IP Addresses and Subnetting
NBG-417N User’s Guide
208
As these two IP addresses cannot be used for individual hosts, calculate the
maximum number of possible hosts in a network as follows:
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 71 Maximum Host Numbers
SUBNET MASK
HOST ID SIZE
MAXIMUM NUMBER OF
HOSTS
8 bits
255.0.0.0
24 bits
2
24
– 2
16777214
16 bits 255.255.0.0
16 bits
2
16
– 2
65534
24 bits 255.255.255.0 8 bits
2
8
– 2
254
29 bits 255.255.255.2
48
3 bits
2
3
– 2
6
Table 72 Alternative Subnet Mask Notation
SUBNET
MASK
ALTERNATIVE
NOTATION
LAST OCTET
(BINARY)
LAST OCTET
(DECIMAL)
255.255.255.0
/24
0000 0000
0
255.255.255.12
8
/25
1000 0000
128
255.255.255.19
2
/26
1100 0000
192
255.255.255.22
4
/27
1110 0000
224
255.255.255.24
0
/28
1111 0000
240
255.255.255.24
8
/29
1111 1000
248
255.255.255.25
2
/30
1111 1100
252