ZyXEL Communications Internet Security Gateway ZyWALL 2 Series - Manual (Page 567)

ZyWALL 2 Series User’s Guide
IP Subnetting I-7
4 255.255.255.240 (/28) 16 14
5 255.255.255.248 (/29) 32 6
6 255.255.255.252 (/30) 64 2
7 255.255.255.254 (/31) 128 1
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 Error! Reference source not found.) available for subnetting.
The following table is a summary for class “B” subnet planning.
Chart I-13 Class B Subnet Planning
NO. “BORROWED” HOST BITS SUBNET MASK NO. SUBNETS NO. HOSTS PER 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