Computer Science - Networking - Discussion

@Sense.

Thank you.

40 subnets + 60 subnets = 100 subnets required.
2^7= 128 which is nearer to 100 subnets.
We know : 1= 128
2= 192
3= 224
4= 240
5= 248
6= 252
7= 254
8= 256
So, Subnet mask will be : 255. 254.0.0.

Thanks all for the explanation.

To accommodate the current and future subnets while allowing the largest possible number of host IDs per subnet, you need a subnet mask that provides a large number of available IP addresses for each subnet.

In this case, you have a Class A network address 10.0.0.0 and want to create 100 (40 current + 60 new) subnets.

To determine the appropriate subnet mask, you need to find the smallest subnet size that can accommodate the required number of subnets (100 in this case) and also provides a sufficient number of host addresses for each subnet.

The formula to find the number of subnets and hosts per subnet is as follows:

The number of subnets = 2^n.
Number of hosts per subnet = 2^(32-n) - 2.

Where "n" is the number of bits in the subnet mask.

Let's calculate for each option:

255.240.0.0(or/1)
Number of subnets = 2^12 = 4096.
Number of hosts per subnet = 2^(32-12) - 2 = 2^20 - 2 = 1,048,574 (approximately).

255.248.0.0 (or/13)
Number of subnets = 2^13 = 8192,
Number of hosts per subnet = 2^(32-13) - 2 = 2^19 - 2 = 524,286.

255.252.0.0 (or /14),
Number of subnets = 2^14 = 16,384.
Number of hosts per subnet = 2^(32-14) - 2 = 2^18 - 2 = 262,142.

255.254.0.0 (or /15),
Number of subnets = 2^15 = 32,768,
Number of hosts per subnet = 2^(32-15) - 2 = 2^17 - 2 = 131,070.

255.255.255.255 (or /32),
This is not a valid subnet mask for general use, as it represents a single IP address with no available host IDs for subnets.

Among the options, the best choice that allows for the largest possible number of host IDs per subnet while accommodating 100 subnets is option 1: 255.240.0.0.

This will provide approximately 1,048,574 host addresses per subnet, which is the highest number compared to the other options.

In 10.0.0.0 , 10 will remain fixed, we need to create 100 subnets, we will require at least 7 bits to uniquely identify each subnet (2^7 = 128 which is > 100),
So in this;
10.(00000000).00000000.00000000, starting 7 bits will be chosen,
i.e., -
10.(11111110).00000000.00000000 = 10.254.0.0.