MadeEasy Workbook: Computer Networks - Subnetting

Question

Consider the following IP address with corresponding subnet mask:

IP add: 172.60.50.2

Subnet mask: 255.255.224.0

What is the range of assignable IP addresses on the subnet on which the host belongs:

a) 172.60.30.0 - 172.60.63.255

b)172.60.32.1 - 172.60.63.254

c)172.60.32.1  -172.60.64.255

d)172.60.32.0 - 172.60.127.254

Comments

AND the subnet mask with given IP to get the Network ID as 172.60.32.0 and OR the complemented subnet mask with the IP to get the direct broadcast address as 172.60.32.255.Hence the assignable range of IP addresses would be 172.60.32.1-172.60.63.254.

Hence,answer is (B).

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I think option (b)

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The logical AND between the subnet mask and the IP address will give the starting address of the network.

When you do that, you'll get the IP as: 172.60.32.0.

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Bt the first and the last address isn't assignable.The 1st address denotes the network address and the last address is the broadcast address.

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Oh yeah, fair enough. I forgot about that. It should be 172.60.32.1, the first assignable address.

Thank you for correcting.

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Logically if we see the question asked assignable IP address.

As we cannot assign X.X.X.0(N/W address) and X.X.X.255(DBA), the remaining option is 'B' :).

Answer 1

Given subnet Mask :- 255.255.224.0 = 1111 1111 . 11111111 . 1110 0000 . 0000 0000

host bits = zero bits in Subnet Mask represent HOST bits ===> no.of host bits = 13

 

if you want Network IP address:- put all zeros in host bits in the given ip.

Given IP Address = 172.60.50.2 = 172.60.0010 0000 . 0000 0000 = 172.60.32.0

 

if you want first host address:- put all zeros in host bits in the given ip except LSB, make LSB as 1

Given IP Address = 172.60.50.2 = 172.60.0010 0000 . 0000 0001 = 172.60.32.1

 

if you want last host address:- put all ones in host bits in the given ip except LSB, make LSB as 0

Given IP Address = 172.60.50.2 = 172.60.0011 1111 . 1111 1110 = 172.60.63.254

 

if you want Broadcast address of this network :- put all ones in host bits in the given ip.

Given IP Address = 172.60.50.2 = 172.60.0011 1111 . 1111 1111 = 172.60.63.255

Comments

@Shaik Masthan 

I guess you need to modify the last line.. The last host address which can't be an assignable IP address...

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@the_bob

Thanks for the correction.

it's a typing mistake ( it occurred due to copy and paste), i will update it.

Answer 2

Yes.. Answer is option B.

Add subnet mask + ip address... You will get subnet id to which this ip belongs to.

Answer 3

Ans  is B