What is Supernetting?
Supernetting is the opposite of Subnetting. It is the process
of combining multiple subnetworks to one. This is also known as
Class Inter-Domain Routing (CIDR). Once we combine multiple
networks to make it a single one then we have an improved
version of routing as we have a less number of routing tables.
We basically modify the subnet mask here to encompass the range
of IP address covered by smaller networks.
Here are some steps to find out the Supernet.
We need to select the contiguous networks you want to combine.
192.168.0.0/24
192.168.1.0/24
192.168.2.0/24
192.168.3.0/24
And then perform the first step to convert them to a binary
format.
192.168.0.0 – 11000000.10101000.00000000.00000000
192.168.1.0 – 11000000.10101000.00000001.00000000
192.168.2.0 – 11000000.10101000.00000010.00000000
192.168.3.0 – 11000000.10101000.00000011.00000000
Determine the common bits which I have been highlighted above.
So we have a common 22 bits which is “11000000.10101000
.000000”. Now the new subnet mask is /22 and our network start
from 192.168.0.0 and ends at 192.168.3.255.
Our Supernet address is 192.168.0.0/22.
Network address: 192.168.0.0
Broadcast address: 192.168.3.255Now we will have less number of routing tables which basically
reduce the processing resources on routing devices. The routing
devices needs to be a very less routing as compared to old
network for Supernet. Let’s understands how it reduces that.
If we have the above four networks (192.168.0.0, 192.168.1.0,
192.168.2.0, 192.168.3.0) and all have a next hope of 10.1.1.1
then for each network’s packets needs to be forwarded via
10.1.1.1 and then we will have below routing table.
Destination Next hope
192.168.0.0/24 10.1.1.1
192.168.0.0/24 10.1.1.1
192.168.0.0/24 10.1.1.1
192.168.0.0/24 10.1.1.1
Now after Supernet you have only this one.
Destination Next hope
192.168.0.0/22 10.1.1.1
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