Cisco Training CCNA IP Addressing - Part 6

[Superfester1959]

Thank You!!!!!!

I am going to study this stuff until It fills my dreams!

You lay this information out so that it is easy to absorb!!!!!!!!!

[kiobubba]

bit lost on this one anychance of doing it again

Love the videos by the way this has explained a great deal to me and learnt more in the past hour than any of the books has explained to me

[crazycutz]

what the hell.. going to fast.... :(

[zozepetas]

Many thanks ,great job .

[TheKevcanning]

How would you work out the broadcast adress of the 42nd and 48th usuable subnet? Given 181.152.241.69 / 26?

[zedonutube]

Mr. Mills, You do have clever way of teaching and making things easy! Many thanks!

[dkniles1]

Mr john Mills,many thank you and respect for your excellent work!

greece

[ssthao]

would it take longer to list all the possible subnets by using the magic number (256) if the subnet mask given is 255.255.255.252? In this case each subnet is an increment of 4 which means you have to go from 0, 4, 8, 12, 16 ... 252.

[RAWagner]

I have another trick for you. There is a direct relationship between the hosts and the mask. If you write down 1, 2, 4, 8, 16, 32, 64, 128 and then match them to their hosts we see that it matches very nicely. 255, 254, 252, 248, 240, 224, 192, 128. Adding any 2 rows together will always equal 256. There are some other relationship tricks we can gather from additional information, but adding this to your training will cut the steps in half.

[LastAxis]

When he says "all the different subnets that can be created with that mask" does he mean that the IP address being the decisive factor as to which subnet is real? (for that given IP?)

[getvickyslove]

great trick! thanks. it is going to help me for my lifetime..

[petromarkus]

Great explanation. thanks a lot.

[musicarena1]

Great Tutorial!! Thank you very much!!

[stananizer]

I understand the process but where does the value of the Magic number come from ? is it always 256 for working with the last octec of the mask or would if change if 240 was different?

[iAmSiklee]

it won't change... that magic 256 number is constant....

[jay444truth]

Small caveat - this trick is gr8 only for the third octet...if the scenario is subnetting in second octet, it's slightly different ball game !!

[krraa]

Wow

[awb17a]

Full marks - your vids are great.

[mistashaft21]

I'll be damned if this guy doesnt make sense.

I am officially impressed

[lafouboy2]

i am a little confused at first, so I go back and watch the video again, and wahla, It makes 75% sense to me (It is hard for me to concentrate, so getting 75% comprehension from me is very freaking impressive).

[kamakazy07]

i never comment on videos...

but i wanted to say thank you very much for doing all of this. Ive watched all your videos and each one help me a bit more than the last.

Thank you!

[ukbakrol]

Thanks. After some practice for question like this you can give answer in less than 20 sec. So whoever is thinking its too hard its not after some practice. So guys, goodluck with it.

[publicuse2]

In many cases you can get away with using .48 as a host.

The routers will just forward the packets to .48 to the right network, so it's a matter of whether the host itself is fussy or not.

If the host is fussy and refuses to allow you to give it a "network address", you might be able to sacrifice connectivity with "neighbouring" addresses by setting an incorrect 255.255.255.224 mask.

[konfetti002]

Host Range is: 48 --> 63

with :

1. 48 ... as Network base Adress

2. 63 ... as Broadcast Adress

anynumber above belongs to Network & between is Host !

right ? or .. left ?? =)

[konfetti002]

that's amazing ! =)

guys you may have to use the calc a paper & practice it ;)

thank you again for these vids ;)

[DnSavior]

I am confused as well. Is not te answer, B, C, and E?

[nicoxis]

Not E, because it is part of 32 subnet, not the 48 subnet segment that 172.16.12.54 is from.

[drakezen]

If the mask is 240 and the ip address is 172.16.12.54 wouldn't that give a subnet host range of 172.16.12.48 to 172.16.12.54? with 172.16.12.55 being the broadcast address.

So how would 172.16.12.64 be a valid host address with this range using that mask?

The question is what are the valid hosts with that mask? I dont think I understand why you are showing what possible subnets are possible.

[HabloIrlandes]

drakezen & DnSavior , .240 gives you a Subnet of .48, here's how long way - When you "Logical AND" 172.16.12.54 & 255.255.255.240 you get 172.16.12.48, that is you "logical AND" 10101100 00010000 00001100 0011 0110 &

11111111 11111111 11111111 1111 0000 -

10101100 00010000 00001100 0011 0000 which translates to decimal to 172.16.12.48. Put all 1's in for the Host portion and it gives you -172.16.12.63 (Broadcast) so range is .49 - .62

[HabloIrlandes]

His "Trick" is ever simpler, just subtract your last octet - .240 from the Magic number "256" and you get 16, this number represents the number of "Steps" in which the subnets increment. So subnets would be 16,32,48,64 etc... However we know that the numbers 16, 32, 48, 64 etc... are the Subnet which means the number preceding it will be the broadcast address for the preceding subnet, so .16's broadcast addy is .32, and we know neither of these are valid as hosts. So .54 is in the range .49-.62

[drakezen]

Ah, much thanks. I understand what he means now. True, its a good trick.

[FILMEfilm]

wow good point

[nowaydudecheckitout]

I listened to a guy who said we shouldn't use "tricks" because of blah blah....but on the test i just took, converting to binary really screwed me time wise. This trick is good, and thanks to this guy i wont spend a ridiculous amount of time converting crap during the test.

[groovekittie]

OMFG YOU ARE MY HERO! Thank you!

[robertfng]

thanks for taking the time to do these..especially the "trick". I understand it now!! 5 Stars!

[jaimapu3]

thanks a lot to post exmaples. it really helps me to understand much better. I wish my teacher could explain subneting like you..

[seree86]

This is great. Makes me want to learn more from your videos. Everything sinks in after the second watch.

[esuvan]

Thanks for the post.

[mitchellcmb]

Thanks for your videos! Your explanations actuallly make sense! This method is great!

[westsan]

Great tip; kudos!

[arm4life87]

will 256 work with all subnet masks to determine the subnet host ranges and broadcast addresses?

[kurizzos]

It would because 256 is the highest amount of address possibilities in one octet: (0 to 255 from all 0s to all 1s). As in the vid, same deal goes with any masking (check equation below): possible octet bits - masked bits = host bits. e.g. 256 - 248 = 8 256 - 240 = 16 256 - 224 = 32 256 - 192 = 64 256 - 128 = 128 etc...

[trantos]

thank you very much keep going u make a great job /

[chicks123]

Thanks for the tip. I'm reading a book and it says to use the magic number where you draw a line between the network bits and the host bits and look at the network bit next to the line. You look at the place value of that bit to see what the increments of the subnets will be. It works, but you still have to write out the binary value of the octet. Your way is much faster.