Zyxel-communications P-660HW-T v2 Manual de usuario descargar pdf (Pagina 299)

P-660HW-T v2 User’s Guide

Appendix F IP Subnetting 299

Subnetting

With subnetting, the class arrangement of an IP address is ignored. For example, a class C

address no longer has to have 24 bits of network number and 8 bits of host ID. With

subnetting, some of the host ID bits are converted into network number bits.

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.

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 mask 255.255.255.128.

The following table shows all possible subnet masks for a class “C” address using both

notations.

The first mask shown is the class “C” natural mask. Normally if no mask is specified it is

understood that the natural mask is being used.

B 255.255.0.0

C 255.255.255.0

Table 132 “Natural” Masks (continued)

CLASS NATURAL MASK

Table 133 Alternative Subnet Mask Notation

SUBNET MASK SUBNET MASK “1” BITS LAST OCTET BIT VALUE

255.255.255.0 /24 0000 0000

255.255.255.128 /25 1000 0000

255.255.255.192 /26 1100 0000

255.255.255.224 /27 1110 0000

255.255.255.240 /28 1111 0000

255.255.255.248 /29 1111 1000

255.255.255.252 /30 1111 1100

1 2 ... 294 295 296 297 298 299 300 301 302 303 304 ... 350 351

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Zyxel-communications P-660HW-T v2 Manual de usuario Pagina 299