ThetaCorp has been assigned three class C network addresses: 188.8.131.52, 184.108.40.206 and 220.127.116.11. You want to combine these addresses into one logical network to increase the number of hosts IDs you can have on your company's network. Which subnet mask must you use?
As its name suggests, supernetting, officially called Classless Interdomain Routing (CIDR), is the inverse of subnetting. When you create a subnet, you break a network ID into subnets; when you create a supernet, you create a larger logical network ID from several smaller network IDs.
In subnetting, you operate on the highest (leftmost) host ID octet, the fourth octet for a class C address. In supernetting, you work on the lowest (rightmost) net ID octet, the third octet for a class C address. Taking the class C addresses 18.104.22.168, 22.214.171.124 and 126.96.36.199 as our example, we convert them into binary:
188.8.131.52 = 11010000.11001001.00000100.00000000 184.108.40.206 = 11010000.11001001.00000101.00000000 220.127.116.11 = 11010000.11001001.00000110.00000000
Seen in binary, we notice that only the last two digits of the third
octet differ (00, 01 and 10).
Therefore, we can safely mask the preceding digits with the supernet
mask 255.255.252.0 (11111111.11111111.11111100.00000000), leaving
the ten-digit addresses 0000000001 through 1111111110 for a continuous
range of host IDs.
Before attempting to implement supernetting,
remember that your routers must also support CIDR.
Your company has been assigned three class C network addresses: 18.104.22.168, 22.214.171.124 and 126.96.36.199. You want to combine these addresses into one logical network to increase the number of hosts IDs you can have on your company's network. Which subnet mask must you use?
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