ZyXEL Communications FSG1100HN User Manual page 116

Appendix B IP Addresses and Subnetting
Subnet Mask - Identifying Network Number
Network Number
Host ID
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.
Subnet Masks
8-bit
mask
16-bit
mask
24-bit
mask
29-bit
mask
Network Size
The size of the network number determines the maximum number of possible
hosts you can have on your network. The larger the number of network number
bits, the smaller the number of remaining host ID bits.
An IP address with host IDs of all zeros is the IP address of the network
(192.168.1.0 with a 24-bit subnet mask, for example). An IP address with host
IDs of all ones is the broadcast address for that network (192.168.1.255 with a
24-bit subnet mask, for example).
116
1ST
OCTET:
(192)
11000000
BINARY
1ST 2ND
OCTET OCTET
11111111 00000000
11111111 11111111
11111111 11111111
11111111 11111111
2ND 3RD
OCTET: OCTET:
(168) (1)
10101000 00000001
3RD 4TH
OCTET OCTET
00000000 00000000
00000000 00000000
11111111 00000000
11111111 11111000
FSG1100HN User's Guide
4TH
OCTET:
(2)
00000010
DECIMAL
255.0.0.
255.255.0.0
255.255.255.0
255.255.255.248