CCNA subnetting question

delford33

Hi,

I have a question regarding subnetting. The question is

The 213.115.77.0 was subnetted using a /28 subnet mask. How many usable subnets and host addresses were created as a result of this.??

The book which I am using says the answer is 14 networks and 14 hosts.[/b]

I cannot understand this. why do we have 14 networks. We are using 4 bits for the host portion. I thought this would mean we have 16 subnets. I agree that we have 14 hosts per subnet.

Any help would be very much appreciated.

davenport

That would depend on your network equipment. Modern equipment would have 16 networks. Older equipment would only have 14. Older equipment can't use all 0's or 1's . You can do some research on the RFC for ip subnet-zero and that will give you more detail.

delford33

Thank you,

This is supposed to be a typical question on the CCNA exam and I must choose one of the following to be the correct answer.

2 networks 62 hosts
6 nets 30 hosts
16 nets 16 hosts
62 nets 2hosts
14 nets 14 hosts


The question and many many more subnetting questions do not refer to the type of equipment.

My study material always said that 2^x networks (where x is number of bits used for the network and 2^y-2 hosts where y is number of bits used for the hosts.

davenport

Do you know when your material was released? Most of the books I've read, and the video's I've watched all assume the use of Ip subnet zero. The cisco tests assume this as well. You can read more about it here:
http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a0080093f18.shtml

davenport

I meant to add. You're right about the question above. It would be 16 networks, and 14 hosts. When you are taking the exam it will more than likely tell you that Ip subnet zero is in use. That way you'll know not to subtract 2 from your networks.

ETA: No problem at all. Just hope this helps.

delford33

Thanks very much for the clarification. It may be pretty old the material that I am using,I understand what you are saying so thanks again.