Magic Number Subnetting - N10-008 CompTIA Network+ : 1.4
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- เผยแพร่เมื่อ 28 ก.ย. 2024
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The “Magic Number” process of IP subnetting is a popular shortcut that requires a minimal amount of math. In this video, you’ll learn the magic number method and how to optimize the method during an exam.
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I have an allergy with subnetting but seeing your videos makes it easier now for me. Thank you
coming into this studying thing I knew subnetting would be the most difficult part for me to get, but here you are teaching it with ease and expertise. Thanks a lot for this amazing way of subnetting
Based
Thank you once again for making this technical subject matter make more sense.
After some practice, I understand this method better now and this is awesome! Total game changer
Thank you so much. This is even faster than Seven Second Subnetting.
Wow! An interesting approach. Thank you for posting. Your content is always fantastic. Your videos are the main reason I was able to pass the CompTIA trifecta exams on my first attempt. Thank you for all that you do, Professor. Cheers!!
hey did you pass N+ 008 or 007?
@@Potatoslice 007
@@Intrepid344 @potatoslice -- was this your only source?
was this your only source?
Thanks for everything professor currently using your vids to study for core 1!
When calculating the magic number, why is it -256 rather than 255?
There are 256 possible numbers in each octet (0 through 255).
@@professormesser This makes so much sense, thank you for your constant effort teaching us!
Zero also counts as a number
waaaaaaaaaaaay faster than 7 second subnetting thank you sooo much
Love the bridges
Well explained better than the textbook.Thanks
For the one problem....why do we do 176 instead of 184? These between numbers are going to jam me up come test time.
Thanks Professor! This has helped me a lot.
Thank you so much Professor
I have so many questions about this. How does DHCP handle out the request and knowing which subnet to give it to? Why not use a router to divide a network instead of this all this?
is it really worth creating charts before the exam spend valuable time to then get 1 question on subnet calculation?
Exactly like there has to be a faster way then creating that huge chart for the magic number. He said we wouldnt need it but proceeded it to use smh
@antoniogray1417 I just dont get why wouldn't we be allowed to use a simple Windows calculator for something like this? Like is comptia testing us on subnetting knowledge or ability to do complex math in our heads? 😕 imagine a real-world scenario: your company gives an assignment to create 3 subnets for the network, BUT you can't use the calculator....
@@xFlow777y u cant use a calculator for this, i get subnet calculators but why not normal ones?
At 0:49, there is a typo where a CIDR /31 lists "Hosts per Network: 1" --- this is incorrect because the number of usable hosts per network for CIDR /31 should be 0, right?
From a binary math perspective, you're absolutely right. A /31 mask isn't useful on a typical network.
This is outside the scope of the Network+ exam, but there is RFC 3021 which provides a way to use a /31 on a link with only two devices (such as a point-to-point WAN link). The two devices would need to support RFC 3021, but I think it's an interesting quirk of networking.
Professor Messer, regarding the slide at 0:36, how do you determine that a /24 mask creates 1 network?
That's the starting point for the subnetting, so it's one big network until we start cutting it up into smaller pieces.
@@professormesser thank you so much Professor
I can subnet class C very well. Its the class A and B subnetting I have a little trouble with.
Can anyone explain how Prof Messer got subnet ID 64 after he found that the "magic #" was 16 (256-240)? That seems to be my only hang up with the magic number process. Thanks in advance if anyone answers!
Loved this lesson!
Yayyyy
Hello Professor, in the minute 4.55, what do we mean by "the interesting octet"? Thank you for your reply
What if the interesting number is an odd number or doesn't land right on the charts?
Hi everyone. I'm just starting to study for my Network + and had a question about this video that I'm hoping someone here can help me with. At 16:55 "Speeding up the magic" the IP address came with a CIDR number of /27 and made it possible to use the chart. But in earlier parts of this lesson, the IP addresses did not come with a CIDR number. How would I be able to use this chart if I was just given an IP address without CIDR, or is it even possible? If the IP address was not given a CIDR number, would I then need to revert to the slightly slower Magic Number method in the earlier part of this video? Any help would be greatly appreciated. Thanks!
I got it, just need to get quick once I get the magic number, but I understand the concept and can do the math
Excellent.
After watching all the video, I came to the conclusion that the magic number is the number of hosts. Is that right? Can someone confirm?
A bit late but I think the magic number represents the top level number/address available for each subnet of that particular octet while 2^x - 2 where x is total hosts bits (all of the 0's) means total hosts available per subnet.
I'm more than likely confusing myself but please correct me if wrong.
Gotta love how people say subnetting is hard. This is ridiculously easy. Thanks Messor for making it easy.
256!! IT"S MAGIC!!
Legendary
what if the magic number is an odd number
This method completely makes sense. It's still the strangest thing to me when a range doesn't start with 0 and end with 255 but I can come up with a random IP address and subnet and do them math within a minute or so to get all the important information. If you practice for half an hour doing the math becomes pretty easy, checking with a subnet calculator really helps to confirm you're doing it right.
I know you get this a lot on every video but thank you for making it easier to understand.
I'd like to say that I've passed my Security+ exam thanks to your videos. I guess I'm now going backwards down the trifecta and working on my Network+
@@8080VB No I went straight to Sec+ because I already had a bit of background in Networking but as I was job hunting I ended up knocking out Net+ as well
Same here.. reverse trifecta
Thats me to kinda
-- started with Security Plus --- then I was like -- nah -- let me get the Network Plus first then go to Sec so it makes more sense to me. Congrats...
I have my A+, Sec+, Pentest+, and CASP+. I struggle with subnetting. I do worse with magic numbers as he shows them than just doing the math. Smh.
Same here. Lol
This is how my teacher taught us subnetting. He calls binary the horizontal magic numbers and subnetting the vertical magic numbers. Glad to see this on TH-cam helping people because it helped me a lot last year! Thanks as always James!
There can be anywhere from 100 to 120 questions on the CCNA exam, and they only allow you 120 minutes. That's not much time. Thanks, Prof Messer for this video.
I think i'm an idiot this is taking me forever to understand
Thank you Professor! I have struggled a lot in the whole process of calculating IPs, but then I found your vidoes, and things have got way much easier gradually.
You are amazing.. I really appreciate the work you do here. I have struggled with following a written explanation in text book via COMPTIA.. And i thought I was just stupid.. Have got more out 6 hours of viewing your video than 5 weeks of going through COMPTIA's info.
Thanks.
PRof Messer still doing it in 2021, great video !!
In as much as i already knew this different shortcuts and do them severally in my head. I admire the effort you put into detailing it to the public. not anyone could have revealed such magic secret easily.. Prof Messer simply the best
You are the Man for teaching this! Binary math subnetting is too slow and nobody has time for that on a cert exam.
I never thought that this would make sense to me but your explanations cleared it all up.
Appreciate it!
Does anyone know if they hand out calculators when going in person testing..?
Thank You SOOOOOO much. I get it now.
For the subnet problem on 10:15, I calculated the number of subnets and hosts using the longer method of subnetting you shared in the previous video, and I got a total number of 16 subnets along with 4094 hosts per subnet. Why is it here that you are claiming 16 hosts per subnet?
can you write down the chart on the white board prior to the exam ?
I don't know anyone who was used a white board but if you bring a blank piece of paper you are allowed to write down any charts from memory you would like. Ask your proctor or more so let them know you plan on jotting some notes down.
For my A+ exams I got given a whiteboard each time at the testing center.
I don’t understand how to apply this or the seven second method to that test-like question in the beginning.
How do you know a CIDR of /25 gives you 2 subnets? We didn't have any IP addresses with any class for us to figure that out!!
Very interesting to learn about. I enjoy math and can already see different tricks and shortcuts to use to make this manageable and to calculate it relatively quickly.
boom! You are incredible, mate! Now just need a way to get to the higher factorials of 8 and 4 in my head:)
This is an awesome method! I would also like to hear the experience of folks who have taken the online version of the exam. I suppose scratch paper is not allow and does it make things tricky to do the calculations on the "whiteboard" at the screen"? (i suppose there's one) It seems that that's harder to "write" freely in that way. Thanks!
I was wondering this too. Following for a response
To make it clear, given an ip and a subnet mask with this method we can calculate to which subnet the ip belongs?
Wow!!! You explained that topic so easy to understand! !! A++
Interesting methods! Thank you Professor 🥰
Thank you for sharing, this video really helped me!
Thank your professor messer for always keeping your content free for people!
You're a genius! 💞💞🙏🙏
This is a really great tutorial on magic number subnetting, but there is only one thing that Im confused about. On the second magic number example, why is the subnet ID 176 and not 184? Do you always round down in the address block range when calculating this? Thank you.
The first address in a block specifies the subnet. In this example starting at 14:07, the IP address was in the middle of the range 176 through 183, so we would select 176 as our starting (or subnet) address.
Now I get it!
As always, this is an excellent presentation, sir. You have personally helped advance my career considerably over the past decade.
That said - is there a way to quickly extrapolate the number of hosts from this method?
Had to look this over real quick; I'll be taking my exam tonight at 8:45!
How'd it go?
Magic numbers are right up a computer wizards alley!
🦾🧙♂️🌌⌨️
This finally made it click. Thank you.