Calculating The Number Of Subnets And Nodes - D-Link DES-3326 User Manual

DES-3326 Layer 3 Fast Ethernet Switch User's Guide
address. Addresses of all "0"s and all "1"s are reserved for the local
network (when a host does not know it's network address) and for
all hosts on the network (the broadcast address). This also applies
to subnets. A subnet address cannot be all "0"s or all "1"s. A 1-bit
subnet mask is also generally not allowed.
It is important to know how many subnet addresses and how many
node addresses within
implementing an address scheme.
Calculating the Number of Subnets and
Nodes
The number of subnet and node addresses available for a given
addressing scheme can be calculated using the formula:
2 -2 = Number of nodes or subnets
n
Where n = the number of bits in either the subnet mask (to
determine the number of subnets) or the number of bits in the node
part of the IP address (to determine the number of nodes).
Multiplying the number of subnets by the number of nodes gives
the total number of IP addresses available for the entire network.
Note: Subnet masks with non-contiguous mask bits are allowed,
but not recommended.
For example:
00001010.00101010.01001001.11010010
Class A IP address
11111111.11100000.00000000.00000000
Subnet Mask
00001010.00100000.00000000.00000000
Network Address
Switch Management and Operating Concepts
a subnet will be available when
10.42.73.210
255.224.0.0
10.32.0.0
73