ZyXEL Communications 645R-A Series User Manual
Prestige 645R-A Series User’s Guide
IP Subnetting
B-7
Chart B-12 Class C Subnet Planning
NO. “BORROWED” HOST BITS
SUBNET MASK
NO. SUBNETS NO. HOSTS PER SUBNET
1 255.255.255.128
(/25)
2
126
2 255.255.255.192
(/26)
4
62
3 255.255.255.224
(/27)
8
30
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.
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 Chart B-1) available for subnetting.
octets (see Chart B-1) available for subnetting.
The following table is a summary for class “B” subnet planning.
Chart B-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