Route Summarization question??

Any tricks to solving this type of problem quickly. I really don't want to right all the ip routes in binary. Then solve problem.

What is the "Magic trick" besides doing it the long way.

I tried looking on YouTube, but everyone teaches it the long way. I know someone out there figure a quicker way.

Writing stuff out in binary takes way to long for me. My binary number probably wont even line up when done

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Comments

lantech

It's just something that you are going to have to learn. I've never seen an easier way to do route summarization.

Course if you want to come up with an easier way to do it any make a ton of money for it that would be great.

chmorin

Binary isn't so hard once you get your head wrapped around it. That is the only method I know as well. For the amount of times I've had to use it in real world, it works just fine.

networker050184

Once you learn the block sizes it becomes a little easier to do it in your head without the binary notation.

kmusk01

Use this to help your skills: Practice Subnet Skills: Summarize a VLSM Network

I can do it in my head by using "block sizes". I basically look for what which octet all the action is going on in. Then starting at the lowest number I count block sizes until I just pass the highest number.

Exampe:

172.30.48.0/21
172.30.56.0/22
172.30.60.0/23
172.30.62.0/24
172.30.63.0/25
172.30.63.128/30
172.30.63.132/30
172.30.63.136/30

Answer would be: 172.30.48.0/20 (255.255.240.0)

Why, because in the 3rd octet is where the action is taking place. So thinking about block sizes what block works between the first number of 48 and the last number of 63? A block size of 16 works. So now we need to count to get the subnet mask.
Octet 1 = No change so its 8 (255)
+
Octet 2 = No change so its 8 (255)
+
Octet 3 = Change of 4 (240)

Octet 4 = No need to worry about cause the first change in numbers happened in Octet 3.

I am sure there is a better way to explain, but using that link I posted should help you out more. I use block sizes for pretty much all my subnetting. Once you learn those it becomes very easy, at least for me it did.

Ken~

goldenlight

binary is not hard for me. Its writing the info out neat enough to look at

. Plus the time constraint on the test.

WiseWun

As kmusk01 pointed out, the action is taking place in the 3rd octet meaning the first and second is the same. (172.30.) Forget about the last octet, doesn't mean a thing in this case. Next step would be to convert decimal to binary. Again the focus is on the 3rd octet. Once you have completed this step, see where the bits differ. In this case, I have inserted a pipeline. Now add all the network bits borrowed. We know the first and second octet are fixed meaning all 8 bits were used. Now for the 3rd octet, add 4 more bits. Thats 8+8+4=/20.

Decimal Binary

172.30.48.0 172.30.0011|0000.00000000
172.30.56.0 172.30.0011|1000.00000000
172.30.60.0 172.30.0011|1100.00000000
172.30.62.0 172.30.0011|1110.00000000

I hope this was informative.

goldenlight

Wow I must be burned out! First thing I thought of was putting all the octets in binary form. But Now my stategy is to just put the decimal in question in binary form.. Finishing Chp and taking 1 week off from Studying.

Legacy User

I heard about the "magic trick" you subtract something from 255 sounded confusing as hell when it was explained to me. I rather chart out class C seems plain and simple that way. Keep practicing I kept doing examples until I could do class C in my head.