CIDR and address aggregation (a) If a subnet has a IP address range in CIDR form

Question

CIDR and address aggregation

(a) If a subnet has a IP address range in CIDR format of 192.168.2.0/25,

- How many IP addresses are available in this space?

- Of this address space, if one address is reserved for the gateway and one is reserved as broadcast address, the maximum number of hosts this subnet can accommodate is _______.

(b) Suppose you are given an IP space prefix of 111.222.2.0/24, and you need to divide them and assign them to 4 groups. Each group should have the same number of IP address space and can accommodate the same number of hosts. List the 4 consecutive IP address blocks and write them in CIDR formats. How many IP addresses are allocated to each group?

Explanation / Answer

Dear STudent,

here are the answers...

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Ans: A

The given IP address 192.168.2.0/25 belongs to class C address.

The CIDR notation is 25 it means 25 bits are resevered to represent network.

Remaining bits will represent hosts

hence host bits = 32 - 25 = 7

Formul to calculate total hosts = 2N ( here N is the total host bits.)

hence

IP addresses are available in the given space = 27 = 128

since one address is reserved for the gateway and one is reserved as broadcast address.

hence

maximum number of hosts the given subnet can accommodate is = 128 -2 = 126

Ans = 126

-----------------------------------------------------------------------------------------------------------------------------------------Ans: Ans: B

The given IP space prefix = 111.222.2.0/24

If we want to create four groups i.e subnets then we need to borrow sum bits from the host bits.

CIDR notation = /24 it means 24 bits are reserved for network.

to create 4 subnetwork let's borrow 2 bits.

then total subnets = 22 = 4

CIDR notation become = /26

subnet mask = 11111111.11111111.11111111.11000000

                    = 255.255.255.192

block size = 256 - 192 = 64

host bits = 32 - 26 = 6

hosts per subnet = 26 = 64 - 2 = 62

hence

4 consecutive IP address blocks are follwing..

and finaly

Number of IP addresses are allocated to each group = 64 - 2 = 62                 Ans...

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Kindly check and Verify Thanks..!!!

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