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Subnet Mask
WHAT IS IT ?
Subnetting:
-
Dividing a large network into multiple small networks is called subnetting.
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Subnetting enables the network administrator to further divide the host part of the address into two or more subnets.
Local Network Area
Subnet Mask:
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Used to determine what subnet an IP address belongs to.
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It's called a mask because it can be used to identify the subnet to which an IP address belongs by performing a bitwise AND operation on the mask and the IP address.
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The bits for the network address are all set to 1,
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eg.
Subnet Mask
255.255.240.000 (Class B)
11111111.11111111.11110000.00000000
AND
Operation
150.215.017.009
IP Address
10010110.11010111.00010001.00001001
Subnet Address
150.215.016.000
10010110.11010111.00010000.00000000
The subnet mask =
The network address +
The bits reserved
for identifying the subnetwork
CIDR:
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Classless Inter-Domain Routing, sometimes called supernetting, is a way to allow more flexible allocation of Internet Protocol (IP) addresses than was possible with the original system of IP address classes.
192.168.10.0 /25
CIDR notation
(Classless Inter-Domain Routing)
Default Subnet
255
1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1
255
1 1 1 1 1 1 1 1
255
0 0 0 0 0 0 0 0
0
Subnet Mask
255
1 1 1 1 1 1 1 1
255
1 1 1 1 1 1 1 1
255
1 1 1 1 1 1 1 1
128
1 0 0 0 0 0 0
NETWORK 1
NETWORK 2
192.168.10.128
192.168.10.129
192.168.10.130
​.
.
192.168.10.254
192.168.10.255
Number of IP addresses can be assigned
host.
Broadcast ID
Network ID
192.168.10.0
192.168.10.1
192.168.10.2
​.
.
192.168.10.126
192.168.10.127
128 - 2 = 126
2 =
7
n
2 = 128
2 =
1
n
2 = 2
No. of Network:
​
​
​
No. of IP addresses on each Network:
​
​
​
No. of Hosts in each Network:
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