ماالفرق بين Route summarization و CIDR

السلام عليكم
عندي سؤال وهو ماالفرق بين Route summarization و CIDR

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و عليكم السلام

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

For example
172.12.0.0/16
172.13.0.0/16
172.14.0.0/16
172.15.0.0/16

Can be combined to form larger classless block with IP address 172.12.0.0/14

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):

172.16.12.0/24
172.16.13.0/24
172.16.14.0/24
172.16.15.0/24

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.

you need to think about your subnets which you will create , you need to make it in order" achieve common sharing bits " to make aggregation happen
once your CIDR which descriped in blockes by Amna done , this summarization route will be sent to other route in your network

but you must use one of routing protocols which will support classless routing or which send the subnetmask with route updating " OSPF ,EIGRP , RIP v2 , ..."

this situation must have more discussion in CCNP but iam still at CCNA

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