ZyXEL p-660h-61 ユーザーガイド
Prestige 660H/HW Series User’s Guide
Splitters and Microfilters
386
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 (
The following table is a summary for class “B” subnet planning.
Table 140 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