Справочник Пользователя для ZyXEL Communications ZyXEL G-1000 v2
ZyXEL G-1000 v2 User’s Guide
159
Subnetting With Class A and Class B Networks.
For class “A” and class “B” addresses the subnet mask also determines which bits are part of
the network number and which are part of the host ID.
the network number and which are part of the host ID.
A class “B” address has two host ID octets available for subnetting and a class “A” address has
three host ID octets (
three host ID octets (
) available for subnetting.
The following table is a summary for class “B” subnet planning.
Table 78 Class B Subnet Planning
NO. “BORROWED” HOST
BITS
BITS
SUBNET MASK
NO. SUBNETS
NO. HOSTS PER
SUBNET
SUBNET
1
255.255.128.0 (/17)
2
32766
2
255.255.192.0 (/18)
4
16382
3
255.255.224.0 (/19)
8
8190
4
255.255.240.0 (/20)
16
4094
5
255.255.248.0 (/21)
32
2046
6
255.255.252.0 (/22)
64
1022
7
255.255.254.0 (/23)
128
510
8
255.255.255.0 (/24)
256
254
9
255.255.255.128 (/25)
512
126
10
255.255.255.192 (/26)
1024
62
11
255.255.255.224 (/27)
2048
30
12
255.255.255.240 (/28)
4096
14
13
255.255.255.248 (/29)
8192
6
14
255.255.255.252 (/30)
16384
2
15
255.255.255.254 (/31)
32768
1