Sub-Netting Mental Bocks

[SRFlanigan]

OK—I am half way through Cisco, and have done some subnetting. My problem is that I seem to have some sort of mental block when it comes to subnetting. I need to find a site or some darn good book that gives a LOT of practices with the correct answers so that I can cut these mental blocks down to size.

I need a book that gives examples in all classes, mainly classes A-C, obviously.

I am aware of the site “Learn to Subnet,” and am looking for other extensive text/AV tutoring guides. Hey—We all have our blocks, right!

Thanks in advance for any suggestions!

Steve
Home: SRFlanigan@home.com
Work: Steve@regionalinternetmedia.com

DILBERT FOR PRESIDENT!

 

[wybnormal]

Steve- what is the precise block you are having? I might be able to help focus on it a bit better

MikeS "Diplomacy; the art of saying 'nice doggie' till you can find a rock" Wynn Catlin

 

[jeter]

check out this site.

http://www.learntosubnet.com

and listen to any and all that wybnormal has to say on the subject. Jeter@LasVegas.com
J.Fisher CCNA

 

[gfunk123]

Try Daryls TCP/IP Primer at

http://www.tcpipprimer.com,

I think its pretty good - Has a subnet calculator too !!

 

[Guest_imported]

Subnetting is fairly easy after you understand the metods of binary! Look ~

The first step is to write the powers of binary(2 to the power of x)

7 6 5 4 3 2 1 0
128 64 32 16 8 4 2 1

The top row is the power at which 2 is multiplied by. The bottom row is the answer of 2 to the power of x.

And now you study what I call the subnet calculator.~

7 6 5 4 3 2 1 0 (2x)
128 64 32 16 8 4 2 1 (Binary)
128 192 224 240 248 252 254 255 (+ Binary)

As you Know the top row and the middle row are the same as the top, the bottom row is the binary numbers added to each other, for example 128+64=192, 192+32=224.... This step will come in handy in the following steps.

Ok now say that you have an IP address of 192.168.1.0, this is a Class C address, so the first 3 octects are reserved for the network, the last octect is for the hosts

And say that you were given a subnet mask of 255.255.255.224
in binary this would look like ~

11111111.11111111.11111111.11100000

In the last Octect you have 3 1's, resenting the netowrk and 5 o's representing the hosts.

Taking the simple mathematic calulation of 2x-2=x, so for the network 2 to the power of 3 - 2 = 6, 6 resenting the amount of networks you can have and 2 to the power of 5 -2 = 30, representing the amount of hosts per network.

Now here you have 6 total networks with 30 Hosts to each of these networks.

Figuring out network IDs and Host Ids ~

Okay now knowing that you are working with a class C and that the subnet mask is 255.255.255.224 ~
11111111.11111111.11111111.11100000(Binary)

This is where my subnet calculator comes in handy ~

Okay now by looking at the subnet mask in binary you can see the the network ID are the 1's, there are three ones, correct? Now look at the Subnet Calculator ~

7 6 5 4 3 2 1 0 (2x)
128 64 32 16 8 4 2 1 (Binary)
128 192 224 240 248 252 254 255 (+ Binary)

The third one over from the left is 32! Correct??

7 6 5 4 3 2 1 0
128 64 32 16 8 4 2 1
128 192 224 240 248 252 254 255

1 1 1 0 0 0 0 0 (last Ocetect in Binary)

Now 32 will resent the steps to get the network IDs, go in 32 increments.

Example ~
32 64 96 128 160 192

These are the 6 network IDs for your network.

Easy HUH??

and for the host Ids you simple tell your self +2-1, Okay now 32+2-1=33, 64-2=62 (This is the range of hosts for your first network, 63 being the broadcat and the 64 being the netowrk ID for network #2.

Network IDs Host Ids Broadcasts

32 33 - 62 63
64 65 - 94 95
96 97 - 126 127
128 129 -158 159
160 161 - 190 191
192 193 - 222 223

And 224 is the last octect in your Subnet mask!
There i Just taught you how to subnet, Please Print this out and read and study it! It will help you greatly!!!!! If you have any further questions please e-mail me at
Skee69@hotmail.com

Thank you,
Cory J.