ZyXEL P-661H-D1 User Guide - Page 285

Network Size, Table 87

Page 285 highlights

Appendix A IP Addresses and Subnetting 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 87 Subnet Masks BINARY 1ST OCTET 8-bit mask 11111111 16-bit mask 24-bit mask 29-bit mask 11111111 11111111 11111111 2ND OCTET 00000000 11111111 11111111 11111111 3RD OCTET 00000000 00000000 11111111 11111111 4TH OCTET 00000000 00000000 00000000 11111000 DECIMAL 255.0.0.0 255.255.0.0 255.255.255.0 255.255.255.248 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). As these two IP addresses cannot be used for individual hosts, calculate the maximum number of possible hosts in a network as follows: Table 88 Maximum Host Numbers SUBNET MASK HOST ID SIZE 8 bits 16 bits 24 bits 29 bits 255.0.0.0 255.255.0.0 255.255.255.0 255.255.255.248 24 bits 16 bits 8 bits 3 bits 224 - 2 216 - 2 28 - 2 23 - 2 MAXIMUM NUMBER OF HOSTS 16777214 65534 254 6 P-661HNU-Fx User's Guide 285

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Appendix A IP Addresses and Subnetting
P-661HNU-Fx User’s Guide
285
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.
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).
As these two IP addresses cannot be used for individual hosts, calculate the
maximum number of possible hosts in a network as follows:
Table 87
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
24-bit mask
11111111
11111111
11111111
00000000
255.255.255.0
29-bit mask
11111111
11111111
11111111
11111000
255.255.255.248
Table 88
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
255.255.255.248
3 bits
2
3
– 2
6