An ISP has a block of addresses with the starting address 117.5.12.0/24. This IS
ID: 3573584 • Letter: A
Question
An ISP has a block of addresses with the starting address 117.5.12.0/24. This ISP has to assign IP addresses to four small ISPs in subblocks such as:
a) one subblock of 65 addresses,
b) one subblock of 64addresses,
c) one subblock of 12 addresses and
d) one subblock of 5 addresses
Provide the first and last IP addresses for each of the above subblock. Briefly, explain each of your answers. Note that each IP address you mention should contain the “Prefix” and the “Suffix” parts. (use your own word not copy paste pls)
Explanation / Answer
Dear Student here is the complete answer of the above asked question...
The given IP address = 117.5.12.0/24
The given IP address belong to Class A address.
The default subnet mask for class A is 255.0.0.0.
Binary notation of 255.0.0.0 is 11111111.00000000.00000000.00000000.
but the given address has 24 mask bit so..
Subnet mask will be 255.255.255.0
Binary notation of 255.255.255.0 is 11111111.11111111.11111111.00000000.
It means that 24 bit for network and rest bit for host(bit=1 i.e Network, if bit=0 i.e Host).
Now we want to create 4 subblock from the given address.And subblock 1 and 2 has 65 and 64 host to connect respectivily.And subblock 3,4 have 12 and 5 host to connect repectively.
Below is the solution...
Answer....
To create Subblock-1 and Subblock -2
In the subblock 1 and subblock 2 ISP provider want 65 and, 64 addresses respectively. So Host bit must be more. So create a network in which we can have 65 and 64 addresses.We can borrow 1 bits from the Host bit to create subnetwork.
IF i borrow 1 bit then the mask will be 11111111.11111111.11111111.10000000
Subnet = 2N=21=2 subnet
Block size (256 - subnet mask) = 256 - 128 = 128.
Valid subnets ( Count blocks from 0) = 0,128
Total hosts (2H) =27= 128
Valid hosts per subnet ( Total host - 2 ) = 128 - 2 = 126
Subblock-1
The network address for Subblock 1 is: 117.5.12.0/25
The first usable IP address for subblock 1 is: 117.5.12.1/25
The last usable IP address in Subblock 1 is : 117.5.12.126/25
The broadcast address in Subnet 1 is : 117.5.12.127/25
Please Note- Prefix=117.5.12.127 and Suffix=/25 (For ex..)
Subblock-2
The network address for Subblock 2 is: 117.5.12.128/25
The first usable IP address for subblock 2 is: 117.5.12.129/25
The last usable IP address in Subblock 2 is : 117.5.12.254/25
The broadcast address in Subblock 2 is : 117.5.12.255/25
To create Subblock-3
In the subblock 3 ISP want to connect 12 host per subblock. So Host are less. So create a network in which we can connet 12 host.We can borrow 4 bits from the Host bit to create subnetwork.
IF i borrow 4 bit then the mask will be 11111111.11111111.11111111.11110000
Subnet = 2N=24=16 subnet
Block size (256 - subnet mask) = 256 - 240 = 16.
Valid subnets ( Count blocks from 0) = 0,16,32.......256.
Total hosts (2H) =24= 16
Valid hosts per subnet ( Total host - 2 ) = 16 - 2 = 14
Subblock-3
The network address for Subblock 3 is: 117.5.12.0/28
The first usable IP address for subblock 3 is: 117.5.12.1/28
The last usable IP address in Subblock 3 is : 117.5.12.14/28
The broadcast address in Subblock 3 is : 117.5.12.15/28
To create Subblock-4
In the subblock 4, ISP want to connect 5 host per subblock. So Host are less. So create a network in which we can connet 5 host.We can borrow 5 bits from the Host bit to create subnetwork.
IF i borrow 4 bit then the mask will be 11111111.11111111.11111111.11115000
Subnet = 2N=25=32 subnet
Block size (256 - subnet mask) = 256 - 248 = 8.
Valid subnets ( Count blocks from 0) = 0,8,16.......256.
Total hosts (2H) =23= 8
Valid hosts per subnet ( Total host - 2 ) = 8 - 2 = 6
Subblock-4
The network address for Subblock 4 is: 117.5.12.0/29
The first usable IP address for subblock 4 is: 117.5.12.1/29
The last usable IP address in Subblock 4 is : 117.5.12.6/29
The broadcast address in Subblock 4 is : 117.5.12.7/29
Ex........
Prefix = 192.168.0.0 and Suffix = /24 (It is just for example what is Prefix and Suffix in a given Ip address)
Kindly Check and Verify.... Thanks...!!!
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