subnets & mask

Unanswered Question
Mar 23rd, 2008

Hi Experts,

can anybody explain what is the difference between subnet & mask

Router#sh ip route connected

10.0.x.x/x is variably subnetted, 11 subnets, 5 masks

C is directly connected, Serial0/0/0:0

C is directly connected, Serial0/0/0:0

C is directly connected, FastEthernet0/1

C is directly connected, FastEthernet0/0.15

C is directly connected, FastEthernet0/0.14

C is directly connected, FastEthernet0/0.12



I have this problem too.
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Justin Brenton Sun, 03/23/2008 - 23:05

Hello Naidu

A subnet is basically a network divided or split up into there own individual networks. For example a typical Class C private network you can have and Each would be a separate network.

A mask is how you determine the size of the network, and where the network starts, i.e. 10.X.X.0 the ending 0 will indicate it's a network.

a mask for example will let you know how many host and networks you can use with that network mask, for example. if you have a IP address of then the /30 means that you have 30 network bits. Their are 32 bits in a ip address or network mask. 11111111.11111111.11111111.11111100 or Notice how there a 2 0's at the end. These are your host bits.

To figure out how many hosts you can have connected per subnetwork you would use the formula 2 to the power of X. In this example it would be 2 to the power of 2 - 2 . Which equals 2. In this example you would have a mask of You can figure out the mask by using binary.





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