Step 2 - Select A Range Of Addresses For Each Supernet; Supernet Example - 3Com 3C421600A Reference Manual

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PPENDIX DRESSING
Step 2 - Select a
range of addresses
for each supernet

Supernet Example

S
CHEMES
The range of addresses in a supernet must fit exactly into a space that can
be described by its netmask. This means that the zero bits in the netmask
must also appear in the first address of the supernet block. For this to be
true, the third octet in the address must be an even multiple of the same
power of 2 used to form the netmask. For example, if you had created a
block of 8 networks, the third octet in the first address will be an even
multiple of 8. See Figure 4.
Figure 4 Selecting a Range of Addresses
11111100
255.255.252.0
Netmask
The four networks in Figure 5 are all connected to the same Internet
service provider (ISP). The ISP has decided to use supernetting to reduce
the size of his routing tables and improve throughput.
These zeroes must be in the first address
10100000
255.255.160.1
First Address in Supernet