Supernetting???

badboyziggy

I came up on a question about supernetting and i want to know what it is and do i need to know it for the exam. here is the question i came up on

Which of the following /24 subnets can be supernetted into a larger network?
A. 10.10.20.0 /24 and 10.10.21.0 /24 into 10.10.20.0 /23

B. 10.10.21.0 /24 and 10.10.22.0 /24 into 10.10.21.0 /23

C. 10.10.130.0 /24, 10.10.131.0 /24, 10.10.132.0 /24, and 10.10.133.0 /24 into 10.10.130.0 /22

D. 10.10.164.0 /24, 10.10.165.0 /24, 10.10.166.0 /24, and 10.10.167.0 /24 into 10.10.165.0 /22

BryanM67

This is referring to a concept called 'route summarization'. I suggest you find a good CCNA book. I have the 'Cisco Certified Network Associate Study Guide' by Richard Deal. He talks about in detail on pages 508 - 510 and 515 - 518. There may be some online resources on the internet that discuss it but I didn't look. Try googling 'route summarization' and see what you get.

badboyziggy

Oh yeah my bad i just expected a question like that to say summarize in it, i should have thought about a little more

pizzafart

Supernetting is the opposite of subnetting. When you subnet, you take a bigger network and break it into smaller ones. When you supernet you take 2/4/8/16/etc... networks and combine them into a larger one. It gets more detailed than this in practice but I think this is sufficient for your question.

If you understand subnetting then supernetting comes almost immediately. If you're not 100% sure that you understand subnetting then make that a goal before you take the test (you'll fail miserably otherwise). IP addressing using subnets and subnet masks tends to be a hurdle for up and coming CCNA folks. There's a lot of info on the web about subnetting so if one doesn't make sense to you find another until you get it. Even if you think you get it, practice it often until you're able to calculate subnets without too much difficulty.

I can't go into a full-on explination of subnetting, but, let me write you a small chart of valid network numbers. These are just little chunks chosen arbitrarily from within the 0 - 255 octet range. There are many more networks that use the same mask that I haven't written here - up into the 200's and back into single digits. You can guess what they are by observing the increments of change. There are no in-betweens (e.g. 10.10.17.0 /23 would be bogus). Some of the potential answers to the question you posted have invalid network numbers. You'll see that these charts are geared to reveal this. Don't spend too much time with the chart if it doesn't make sense right now - it assumes that you have a certain level of understanding. While studying, it might be fun to come back to it from time to time to see if it becomes more clear. (note: assume that everything begins with 10.10.)

19.0 /24
20.0 /24
21.0 /24
22.0 /24

16.0 /23
18.0 /23
20.0 /23
22.0 /23

12.0 /22
16.0 /22
20.0 /22
24.0 /22

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164.0 /24
165.0 /24
166.0 /24
167.0 /24

160.0 /23
162.0 /23
164.0 /23
166.0 /23

156.0 /22
160.0 /22
164.0 /22
168.0 /22

Once you understand why this chart is full of valid numbers, you might be able to see how some networks can fit in others.

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I came up on a question about supernetting and i want to know what it is and do i need to know it for the exam. here is the question i came up on

Which of the following /24 subnets can be supernetted into a larger network?
A. 10.10.20.0 /24 and 10.10.21.0 /24 into 10.10.20.0 /23

B. 10.10.21.0 /24 and 10.10.22.0 /24 into 10.10.21.0 /23

C. 10.10.130.0 /24, 10.10.131.0 /24, 10.10.132.0 /24, and 10.10.133.0 /24 into 10.10.130.0 /22

D. 10.10.164.0 /24, 10.10.165.0 /24, 10.10.166.0 /24, and 10.10.167.0 /24 into 10.10.165.0 /22

SV

Is the correct answer both A & D

EdTheLad

SV wrote:

Is the correct answer both A & D

Yes A and D, but the problem is this is not supernetting.
Supernetting is the concept of moving the major class boundary to the left.
In this case for instance you have 10.0.0.0/8 network.Since your using /22 it is not considered supernetting but its considered summarization.
In the case you had 192.168.1.0/24 you could supernet this using
192.168.0.0/16, what i've done is i've broken the classful nature of the
class C address.So by making the mask less than /24 its a supernet.
With a class B network address 151.98.25.0/16 if i made the mask less than
16 its also a supernet i.e 151.96.0.0/14
Supernetting is generally used in class C addressing, its a way to assign a block of class C addresses to a customer by using one prefix.

SV

Thanks a lot ed. Its very clear now.