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Simplified Supernetting
An easier way to learn how to supernet is to create a table as follows:
# of Bits (b)
X=8b
# of Networks (2
x
)
1
7
128
2
6
64
3
5
32
4
4
16
5
3
8
6
2
4
7
1
2
Use the above table to you find the number in column 3 that is equal to, or just
greater than, the number of networks you’re needing to combine. (Keep in mind,
though, if you use the next largest increment, you could run into problems if your
organization doesn’t own all the addresses in that range) Notice that the number of
Networks is equal to
2
8b
where
b
is the number of bits used for supernetting.
Example 1
For example, suppose you want to supernet the 16 Class C networks
201.168.0.0 through 201.168.15.0 into a single Supernetted Address Range.
You would find the number 16 in the column labeled
# of Networks
and discover
you need to supernet on 4 bits. This really means borrowing 2 bits from the bits
normally reserved for the network portion of the address.
Since 201.168.0.0 is a Class C address with a Standard Subnet Mask of
255.255.255.0 we know we will be modifying the 3
rd
octet (the last range normally
reserved for network addresses) and using the first 4 bits for our network mask.
In binary, our 3
rd
octet becomes 11110000 which is equivalent to 240 decimal.
Therefore our subnet mask is 255.255.240.0.
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This note was uploaded on 07/22/2011 for the course IT 220 taught by Professor Olson during the Spring '11 term at ITT Tech Flint.
 Spring '11
 Olson

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