ASubnetting Basics

In business, the subnet mask assigned to a device commonly is not the default mask based on the class of IP address being used. For example, at a college, the IP address 10.104.10.88 and subnet mask 255.255.255.0 are assigned to a computer. The 10 in the first octet shows that this is a class A IP address. A class A IP address has a default mask of 255.0.0.0. The 255 in the subnet mask is made up of eight 1s in binary in the first octet (11111111) followed by all 0s in the remaining octets (00000000.00000000.00000000).

The purpose of a subnet mask is to tell you (and the network devices) which portion of the IP address is the network part. The rest of the address is the host portion of the address. The network part of any ...

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