Computer Science - Networking - Discussion

Ans is=A Not B.

IP Address: 192.168.10.0/26.
Subnet Mask: 255.255.255.192.

Number of Subnets: 4,
Number of IP: 64,
Number of Useable Hosts: 62.

Subnet Network First Usable IP Last Usable IP Broadcast
0 ----->192.168.10.0 -----192.168.10.1 ----- 192.168.10.62 -----192.168.10.63
1 ----->192.168.10.64 ----- 192.168.10.65 ----- 192.168.10.126 ----- 192.168.10.127
2 ----->192.168.10.128 ----- 192.168.10.129 ----- 192.168.10.190 ----- 192.168.10.191
3 ----->192.168.10.192 -----192.168.10.193 ----- 192.168.10.254 ----- 192.168.10.255

I am a bit confused with both A and B option. 4=2^2 which means that first 2 bit in the last octet will be used to determine subnet ID but representing 4 in binary we get 100 which is a 3 bit number, so does that mean, we need 3 bits to represent subnet id.

If we need 3 bits than answer will be B.
If we need 2 bits than answer will be A.

Please can any one explain which is correct.

It says that the network supports four(4) subnets --- > 2^N = 4 , so N= 2.

The Network bits(N) are 2, and 6 host bits(H) which points to 11000000 ----> 192 ( in a decimal notation). So the Correct & final answer is : [A] 255.255.255.192.

255.255.255.110000 00.

1*2^7 + 1*2^6 + 0(2^5) + 0(2^4) + 0(2^3) + 0(2^2) + 0(2^1) + 0(2^0).

128+64+(if four subnets is required then we need six-bit because the last 2 is dedicated for HOST and 4 is required).

Hence 255.255.255.192 is the answer.

No.of subnets required - 4.

n bits give subnets 2^n-2.

4 = 2^n-2;

2 < n < 3.

n to be 3 i.e. n/w bits.

Which means last byte of the mask will be 11100000.

255.255.255.11000000.
2^2= 4 subnets, so we use 11.
The remaining 0's for hosts.
So, the answer is 255.255.255.192.

192 = 11000000

No.of subnets= 2^2=4

no.of hosts= 2^6-2=62

So Answer is A

Correct answer is option A.

Please explain it clearly.

I think the answer is A.