Sub-netting:subnet mask is a net mask with the only real difference being that breaking a larger network into smaller parts and each smaller section will use different sets of address numbers. The subnet mask is 32 bit value that usually express in dotted decimal notation used by IP address. This is the combination of net-ID and host-ID.
Example:
Consider the subnet mask as 255.255.0.0. convert the 255.255.0.0 subnet mask to binary.
255.255.0.0 = 11111111 11111111 00000000 00000000 (in binary)
add 1s right after the last 1 on the right (in the middle of the mask, between the 1s and 0s)
I add five 1s to make it look like this:
11111111 11111111 11111000 00000000
Using the subnet's formula, this would give us 25 = 32 networks
Super-netting:
To create a supernetwork, the procedure is to be reversed.Th networks are combined by creating space for a larger number of hosts. To accomplish this, we start with the default subnet mask of 255.255.255.0 and use some of the bits reserved for the Netid to identify the Hostid. The following exampleshows we would create a new supernetwork by combining four separate subnetworks.
Example: If a packet arrives at the router with the destination address
192.168.64.48, the supernet mask 255.255.252.0 is applied to the destination address.
11000000.10101000.01000000.00110000 (destination IP address)
AND
11111111.11111111.11111100.00000000 (supernet mask)
Returns
11000000.10101000.01000000.00000000