Finding Subnet that overlaps

[mmmartin823]

Hello there,

I am studying for my CCENT Part 1 exam and I am struggling with this practice problem.  Could you help me understand the reason for the right answer (D)?  Thank you in advance!

Qt:

R4 has a connected route for 172.16.8.0/22.  Which of the following answers lists a subnet that overlaps with this subnet?

a. 172.16.0.0/21

b. 172.16.6.0/23

c. 172.16.16.0/20

d. 172.16.11.0/25

Thank you!

[jonathanlunt]

Hi Martin

I feel your pain, I struggled to get sub-netting when I started learning networking. I'm not going to give you the answer (would defeat your study) but I will link you to this website which helped me learn it:

http://www.techexams.net/

Sign up, and then browse Cisco/CCNA. Really helped me before I my got CCNA

[agapitca19]

mmmartin823,

It takes practice when it comes to subnetting. you may also find different methods to solve subnetting questions, my advise is find one method or two that makes you comfortable so that when you are either answering questions in practice or actual exam, you are not overwhelmed with thoughts.

To answer your question, this is how i will solve it.

1. Starting from the first octet, count 22 bits for /22. It is in the network of 4 on the third octet(8 bits = 128 64 32 16 8 4 2 1).

2. The network is in increment by 4 as shown below, thus, 172.16.8.0 and 172.16.11.0 are in the same subnet.

    0 - 3

    4 - 7

    8 - 11

    12 - so on and so forth

HTH