8/14/2019 Cisco IP Sub Netting 101

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8/14/2019 Cisco IP Sub Netting 101

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8/14/2019 Cisco IP Sub Netting 101

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subnetting that network. The more 1s that are present in the subnet mask means the more

networks with a fewer number of hosts. The more 0s that are present in the subnet mask

means the fewer networks and the more hosts you have.

In other words, the subnet mask tells routers and computers which portion of the IP address is

for the network and which is for the host. If you slide the line between network and host tothe left, you create fewer networks and more hosts. If you slide the line to the right, you

create more networks and fewer hosts.

How can I write out subnet masks?

You can write out subnet masks in two different ways: dotted decimal notation and slash

notation. The dotted decimal notation method is more than likely what you're familiar with.

This involves writing the numbers and separating them by periods (i.e., dots). For example,

you would write a Class C default subnet mask as 255.255.255.0.

To use the slash notation method, you convert the subnet mask into binary form, writing the

number of 1s in the subnet mask instead. For example, in binary form, 255.255.255.0 would

be 11111111 11111111 11111111 00000000.

In slash notation, this "translates" to /24in other words, the number of 1s. So, you would

write your IP network with its subnet mask like this: 192.168.1.0/24. While the slash notation

method may seem more complicated, keep in mind that it makes diagramming and note

taking easier.