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The idea behind CIDR is that blocks of multiple addresses (for example, blocks of Class B
address) can be combined to create a larger classless set of IP addresses to allow more hosts
Can be combined to form larger classless block with IP address 22.214.171.124/14
Notice that the new mask (/14) is less than the default mask for class B (/16) cause with CIDR we combined multiple class B blocks to create a bigger classless block.
This is done a lot by Internet Service Providers (ISP) for big companies for class C especially, as we running out of class B addresses and many companies will need more than one block of class C as they have more than 254 hosts. The ISP then give them many blocks of class C addresses (say 4 for example) and instead of advertising 4 IP addresses for the 4 blocks they can advertise only one IP address for the whole company using CIDR
Route summarization is generally done within or up to classful boundary:
If you have the class B subnets (it is class B and not C because the first octet 172 is in Class B range):
The above addresses can be summarized to 172.16.12.0/22 notice that the new mask (/22) is still within the default range for class B
The key difference between CIDR and route summarization is that route summarization is generally done within, or up to, a classful boundary, whereas CIDR combines several classful networks.