ZyXEL Communications VMG1312-B Series, Руководство пользователя

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Appendix B IP Addresses and Subnetting
VMG1312-B Series User’s Guide
322
The following t able shows som e possible subnet m asks using bot h not at ions.
Subnetting
You can use subnet t ing t o divide one net work int o m ult iple sub- net works. I n t he following exam ple
a net work adm inist rat or creat es t wo sub- net works t o isolat e a group of servers from t he rest of t he
com pany net work for securit y reasons.
I n t his exam ple, t he com pany net work address is 192.168.1.0. The first t hree oct et s of t he address
( 192.168.1) are t he net work num ber, and t he rem aining oct et is t he host I D, allowing a m axim um
of 2
8
– 2 or 254 possible host s.
The following figure shows t he com pany net work before subnet t ing.
Figure 182 Subnet t ing Exam ple: Before Subnet t ing
You can “ borrow ” one of t he host I D bit s t o divide t he net work 192.168.1.0 int o t w o separat e sub-
net works. The subnet m ask is now 25 bit s ( 255.255.255.128 or / 25) .
The “ borrowed” host I D bit can have a value of eit her 0 or 1, allowing t wo subnet s; 192.168.1.0 / 25
and 192.168.1.128 / 25.
Table 114 Alt ernat ive Subnet Mask Not at ion
SUBNET MASK
ALTERNATIVE
NOTATION LAST OCTET
(BINARY) LAST OCTET
(DECIMAL)
255.255.255.0 / 24 0000 0000 0
255.255.255.128 / 25 1000 0000 128
255.255.255.192 / 26 1100 0000 192
255.255.255.224 / 27 1110 0000 224
255.255.255.240 / 28 1111 0000 240
255.255.255.248 / 29 1111 1000 248
255.255.255.252 / 30 1111 1100 252