Trainsignal and subnetting

Hi everyone,

I 've been watching Trainsignal videos

Does anyone understands how chris Bryant solve problem like this using his method ?

QUESTION: You need to assign a server the last valid host address on the 5th subnet of network 172.16.0.0/19.
What address would you assign?

ANSWER: 172.16.159.254

Because he does not provide any method on how to find the Block size of the subnet using increment for example, and then find all the subnets.

I am really stuck on this

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Comments

SephStorm

all i was able to pick up from his videos was formulas for the # of hosts, # of subnets, and the subnet #, nothing on the actual 1st, last or bcast. if i missed that video, id like to know the name of it.

Ltat42a

In subnetting, you need to know what the CIDR notation represents. /19 = 255.255.224.0. The address is question is a Class B address, and subnetting is taking place in the third octet. You also need to know the block sizes (range multiples) for each bit in the octet.

FloOz

Check out Jeremy Ciora's way of subnetting. Its a very simple method and it will help you tackle any subnetting problem

mella060

Check out the subnetting chapter in Todd Lammles ccna study guide or Jeremy Cioras way of subnetting.

In subnetting, as mentioned above, you need to know what /19 represents in decimal. /19 = 255.255.224.0

The interesting octet is the one where the value is neither 0 or 255, so the 3rd octet in this case. That is where your increment will be.

To find the increment/block size, you can either do 255-224 or find the last bit position where the value is a 1.

For example, /19 in binary is

11111111.11111111.11100000.00000000

Remember with each octet you have....128 64 32 16 8 4 2 1

So the last bit position where the value is a 1 is 32. So the increment is 32 in the 3rd octet

So your networks would be:

172.16.0.0 /19
172.16.32.0 /19
172.16.64.0 /19
172.16.96.0 /19
172.16.128.0 /19
172.16.160.0 /19 and so on

So the 5th subnet is 172.16.128.0/19 and the last usable address in that subnet would be
172.16.159.254

SephStorm

What is the quick way of determining the last usable using this method? (and bcast) Manually counting 32 until some point?

(and what network a host is part of. I need a method that gives me all of the above quickly. So far the odom method gives me the info, but not quickly.)

SephStorm

daras wrote: »

Hi everyone,

I 've been watching Trainsignal videos

Does anyone understands how chris Bryant solve problem like this using his method ?

QUESTION: You need to assign a server the last valid host address on the 5th subnet of network 172.16.0.0/19.
What address would you assign?

ANSWER: 172.16.159.254

Because he does not provide any method on how to find the Block size of the subnet using increment for example, and then find all the subnets.

I am really stuck on this

I found out, this is not in his videos, you have to go to his document, mastering binary math and subnetting, which is distributed not through TS, but through his personal program. Its simple and easy to understand, see if you can send me a message, or an email, something, i'll send you the info. Nothing personal to the people who replied, but he really has a way of explaining it without increments and "block sizes", "interesting bits" you just do the binary comparisons. I just needed to know what to compare to what. which does not appear to be in the TS program.

mella060

SephStorm wrote: »

What is the quick way of determining the last usable using this method? (and bcast) Manually counting 32 until some point?

(and what network a host is part of. I need a method that gives me all of the above quickly. So far the odom method gives me the info, but not quickly.)

I never bothered with Odoms method. I used the method in todd lammles book and jeremy cs cbt nuggets videos. These methods are way easier in my opinion.

After you work with subnetting for a while, you will know your multiples like the back of your hand. Practice, practice practice.

A good idea when learning subnetting is to write everything down on paper. EVERYTHING, bit by bit. That way it sticks in your brain.

atorven

Learn/memorize the table that Ltat42a posted, everything to do with subnetting comes from there.

daras

SephStorm wrote: »

I found out, this is not in his videos, you have to go to his document, mastering binary math and subnetting, which is distributed not through TS, but through his personal program. Its simple and easy to understand, see if you can send me a message, or an email, something, i'll send you the info. Nothing personal to the people who replied, but he really has a way of explaining it without increments and "block sizes", "interesting bits" you just do the binary comparisons. I just needed to know what to compare to what. which does not appear to be in the TS program.

Hi,

Please send me an e-mail with info for subnetting in daragiaa@hotmail.com

Thanks

SephStorm

I just sent it.

Ismaeljrp

I would suggest just, choose a good method. Then, practice and more practice, don't worry about the speed, just repetition. With reps, you'll start to memorize all the patterns, all the increment block sizes, you'll naturally start to feel like it's automatic. Don't get too caught up for now on speed. Just practice, speed will come, because you'll know the knowledge.

Ismaeljrp

Subnetting Quiz -- Steve Kehlet's Pages

I used that, to help get into the habit of reverse engineering without paper. If you can average 40 seconds or less, that includes typing, then I would say you are in very good shape.