ip addressing

Question

A host in a subnet has the IP address 130.83.126.10. How  many hosts can be addressed in network?

Here subnet mask is not given .

please explain brieflly.

Comments

It is a class B network. No information is given for subnets.

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It is made easy workbook problem with numerical type questions....

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I think we can assume entire class B as a subnet and therefore the hosts possible are 2^16-2

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may be there is some other logic.

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Means you are not sure about answer?

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Hmm. :(

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Yes Ashish your way of solving is correct because subnet mask is not given so we'll consider it as class B network with subnet mask 255.255.0.0 which is having $2^{16}$ - 2 hosts.

Answer 1

Whenever the subnet mask is not given, take it according to the class. As here the address belongs to class B so consider the subnet mask as 255.255.0.0

Therefore the answer should be (2^16) - 2. We are deducting 2 as one is used for Net ID and one for DBA.

Answer 2

The IP address 130.83.126.10 falls in Class B. In class B, 16 bits are of Network ID and other 16 bits are of Host ID.

1 0 [This 2 bits are fixed)
Network ID (16 bits)	Host ID (16 bits)

 

As first 2 bits are fixed we are left only with 14 bits in NID. Therefore, Number of networks through Class B = 2^14 = 2^4 * 2^10 = 16K

Similarly, about Host ID, 2^16. But as two IP's from each class are allotted for Direct Broadcasting (here, 130.83.255.255) and one for Network ID (here, 130.83.0.0).

Hence, 2^16 - 2.