Table 267 Class B Subnet Planning - ZyXEL Communications Internet Security Appliance ZyWALL5UTM 4.0 User Manual

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.
A class "B" address has two host ID octets available for subnetting and a class "A" address has
three host ID octets (see
The following table is a summary for class "B" subnet planning.

Table 267 Class B Subnet Planning

NO. "BORROWED" HOST
BITS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Appendix E IP Subnetting
Table 254 on page 690) available for subnetting.
SUBNET MASK
255.255.128.0 (/17)
255.255.192.0 (/18)
255.255.224.0 (/19)
255.255.240.0 (/20)
255.255.248.0 (/21)
255.255.252.0 (/22)
255.255.254.0 (/23)
255.255.255.0 (/24)
255.255.255.128 (/25)
255.255.255.192 (/26)
255.255.255.224 (/27)
255.255.255.240 (/28)
255.255.255.248 (/29)
255.255.255.252 (/30)
255.255.255.254 (/31)
ZyWALL 5/35/70 Series User's Guide
NO. HOSTS PER
NO. SUBNETS
SUBNET
2 32766
4 16382
8 8190
16 4094
32 2046
64 1022
128 510
256 254
512 126
1024 62
2048 30
4096 14
8192 6
16384 2
32768 1
696