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Subnetting

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Class C Valid Host IDs

Here's an example of how to find a valid host ID in a Class C network:

All host bits turned off is the network ID: 192.168.100.0.

All host bits turned on is the broadcast address: 192.168.100.255.

The valid hosts would be the numbers in between the network address

and the broadcast address: 192.168.100.1 through 192.168.100.254.

Subnetting

kay, you've just learned how to define and find the valid host ranges

used in a Class A, Class B, and Class C network address by turning the host
bits all off and then all on. This is very good, but here's the catch: You were
only defining one network. What happens if you wanted to take one network
address and create six networks from it? You would have to do something
called subnetting, because that's what allows you to take one larger network
and break it into a bunch of smaller networks.

There are loads of reasons in favor of subnetting. Some of the benefits

include:

Reduced network traffic We all appreciate less traffic of any kind. Net-
works are no different. Without trusty routers, packet traffic could grind the
entire network down to a near standstill. With routers, most traffic will stay
on the local network; only packets destined for other networks will pass
through the router. Routers create broadcast domains. The smaller broad-
cast domains you create, the less network traffic on that network segment.

Optimized network performance This is a result of reduced network
traffic.

Simplified management It's easier to identify and isolate network problems
in a group of smaller connected networks than within one gigantic network.

Facilitated spanning of large geographical distances Because WAN
links are considerably slower and more expensive than LAN links, a single
large network that spans long distances can create problems in every
arena listed above. Connecting multiple smaller networks makes the
system more efficient.

To create subnetworks, you take bits from the host portion of the

IP address and reserve them to define the subnet address. This means

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