- ZyXEL USB Powered Travel Router Manual

Table 26 Subnet Mask - Identifying Network Number

1ST

OCTET:

(192)

2ND

OCTET:

(168)

3RD

OCTET:

(1)

4TH

OCTET

(2)

IP Address (Binary) 11000000 10101000 00000001 00000010

Subnet Mask (Binary)

11111111 11111111 11111111

00000000

Network Number

11000000 10101000 00000001

Host ID 00000010

By convention, subnet masks always consist of a continuous sequence of ones beginning from

the leftmost bit of the mask, followed by a continuous sequence of zeros, for a total number of 32

bits.

Subnet masks can be referred to by the size of the network number part (the bits with a “1”

value). For example, an “8-bit mask” means that the first 8 bits of the mask are ones and the

remaining 24 bits are zeroes.

Subnet masks are expressed in dotted decimal notation just like IP addresses. The following

examples show the binary and decimal notation for 8-bit, 16-bit, 24-bit and 29-bit subnet masks

Table 27 Subnet Masks

BINARY

DECIMAL

1ST

OCTET

2ND

OCTET

3RD

OCTET

4TH

OCTET

8-bit mask 11111111 00000000 00000000 00000000 255.0.0.0

16-bit mask 11111111 11111111 00000000 00000000 255.255.0.0