Subnet Masking; Calculating The Number Of Subnets And Nodes - D-Link DES-3326SR Manual

For example, the IP address 10.42.73.210 is a Class A address, so the Network part of the address (called the Network
Address) is the first octet (10.x.x.x). The node part of the address is the last three octets (x.42.73.210).
To specify the network address for a given IP address, the node part is set to all "0"s. In our example, 10.0.0.0 specifies the
network address for 10.42.73.210. When the node part is set to all "1"s, the address specifies a broadcast address. So,
10.255.255.255 is the broadcast address for the network 10.0.0.0.

Subnet Masking

A subnet mask can be applied to an IP address to identify the network and the node parts of the address. A bitwise logical
AND operation between the IP address and the subnet mask results in the Network Address.
For example:
00001010.00101010.01001001.11010010
11111111.00000000.00000000.00000000
00001010.00000000.00000000.00000000
The Default subnet masks are:
•
Class A – 11111111.00000000.00000000.00000000
•
Class B – 11111111.11111111.00000000.00000000
•
Class C – 1111111.11111111.11111111.00000000
Additional bits can be added to the default subnet mask for a given Class to further subnet a network. When a bitwise logical
AND operation is performed between the subnet mask and the IP address, the result defines the Subnet Address.
Some restrictions apply to subnet addresses. 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 not allowed.

Calculating the Number of Subnets and Nodes

To calculate the number of subnets and nodes, use the formula (2
mask or the node portion of the IP address. Multiplying the number of subnets by the number of nodes available per subnet
gives the total number of nodes for the entire network.
For example:
00001010.00101010.01001001.11010010
11111111.11100000.00000000.00000000
00001010.00100000.00000000.00000000
00001010.00101010.11111111.11111111
This example uses an 11-bit subnet mask. (There are 3 additional bits added to the default Class A subnet mask). So the
number of subnets is:
3
2 – 2 = 8 – 2 = 6
Subnets of all "0"s and all "1"s are not allowed, so 2 subnets are subtracted from the total.
The number of bits used in the node part of the address is 24 – 3 = 21 bits, so the total number of nodes is:
21
2 – 2 = 2,097,152 – 2 = 2,097,150
D-Link DES-3326SR Layer 3 Switch
10.42.73.210
255.0.0.0
10.0.0.0
n
10.42.73.210
255.224.0.0
10.32.0.0
10.32.255.255 Broadcast Address
189
Class A IP address
Class A Subnet Mask
Network Address
255.0.0.0
255.255.0.0
255.255.255.0
– 2) where n = the number of bits in either the subnet
Class A IP address
Subnet Mask
Network Address