subnetting is my life

mobri09

I have been on the subnet chapter in my CCNA press book for a while now and I don't want to go to the next chapter. Does anyone just love to subnet?

markzab

Pretty soon you'll be able to subnet in your

deneb829

mobri09 wrote:

I have been on the subnet chapter in my CCNA press book for a while now and I don't want to go to the next chapter. Does anyone just love to subnet?

Holy smokes! I hope your not kidding. I seriously love to subnet!

Hey! I bet this is a setup ... you know, like when someone says that they "Simply LOVE John Denver's music!" and you jump up and start screaming "I LOVE John Denver TOO!!". Then everyone in the room laughs at you and calls you a fag .. ahem! Not that it ever happened to ME!

oh, Colorado Rocky Mountain High, I've seen it raining fire in the sky ...

Ed Rooney

It's totally understandable. It's a new skill.

Hint: If you don't want to move on, go learn about IPv6.

Pash

deneb829 wrote:

mobri09 wrote:

I have been on the subnet chapter in my CCNA press book for a while now and I don't want to go to the next chapter. Does anyone just love to subnet?

Holy smokes! I hope your not kidding. I seriously love to subnet!

Hey! I bet this is a setup ... you know, like when someone says that they "Simply LOVE John Denver's music!" and you jump up and start screaming "I LOVE John Denver TOO!!". Then everyone in the room laughs at you and calls you a fag .. ahem! Not that it ever happened to ME!

oh, Colorado Rocky Mountain High, I've seen it raining fire in the sky ...

LOL...nope thats never happened to me either thank god

sprkymrk

deneb829 wrote:

mobri09 wrote:

I have been on the subnet chapter in my CCNA press book for a while now and I don't want to go to the next chapter. Does anyone just love to subnet?

Holy smokes! I hope your not kidding. I seriously love to subnet!

Hey! I bet this is a setup ... you know, like when someone says that they "Simply LOVE John Denver's music!" and you jump up and start screaming "I LOVE John Denver TOO!!". Then everyone in the room laughs at you and calls you a fag .. ahem! Not that it ever happened to ME!

oh, Colorado Rocky Mountain High, I've seen it raining fire in the sky ...

You guys all need to get a life!
Take up something useful like World of Warcraft or something...
Just kidding!
Sorry deneb, had to "unhide" your little John Denver song. :P

Ricka182

Hell, I wish I could subnet in my sleep....then again, I wish I could just subnet to start....I tell myself, someday grasshopper, patience is a virtue, subnetting is a neccessary evil.....

deneb829

Ricka182 wrote:

Hell, I wish I could subnet in my sleep....then again, I wish I could just subnet to start....I tell myself, someday grasshopper, patience is a virtue, subnetting is a neccessary evil.....

There are a bunch of different ways to explain subnetting, but the way it was explained to me is the way I teach it. One thing that I have found is that no matter how it is taught, it is best learned from someone who not only understands it, but can explain it in a way that can be understood - I find that it is also best taught in person 1 on 1. I also don't know anyone who has been able to completely grasp it just from a book.

In the fall semester, I am teaching the Routing and Switching class here at the college. I have had the same bunch of students for many of the network admin classes. I know that there are a few of them who probably just won't get it. Still, I have reserved the first 3 weeks of class for just TCP/IP and am looking forward to teaching subnetting and hope that they all get it.

I mentioned this in another post, but it applies here - When you finally get subnetting, you tend to get it all at once. It's not something you learn over time. In 2000, a coworker taught me subnetting in binary and he stuck with me until I got it. It took about 40 minutes and at times, it felt like my brain was going to explode. But he understood it and he knew that I was getting it.

When I got it, it was seriously a spiritual experience. The instant it clicked, the entire internet topology made sense. In my mind, I saw a packet leave the network out the router in the next room and make its way across the internet. I saw the routing tables and the subnets grow from /24's to /16's to /8's as the packet make its way on to the backbone (255.255.255.0 to 255.255.0.0 to 255.0.0.0) and shrink as the packet made its way back to the smaller networks until it found its destination. I reached a whole new level of geek that day and while I don't remember the exact date, I consider the moment I understood subnetting to be one of the most significant days of my career.

Thinking about learning subnetting at some point in the future is akin to visiting the dentist for a toothache at some point in the future. When you are ready to learn it, get with someone who is willing to teach you and don't leave the room until you understand it. If you don't get it in that sitting, you won't get it later. You'll have to sit with someone else and try again. I guess it's like taking a test.

Sulblk27

Very inspiring deneb829, I'm one of those that are barely hanging on by a thread...for some reason Class A is killing me... I had to put the book down for the last two days, and figure I would take another stab at it... the part that makes my brain freeze is 255.255.0.0. Just when I think it clicks (ie- the second octet is a 'block' of one...so when I first host is asked for--it's 10.0.0.1 then 10.1.0.1) I can't figure out why the one moved to the second octet...
But off to figure it ...

markzab

Sulblk27 wrote:

Very inspiring deneb829, I'm one of those that are barely hanging on by a thread...for some reason Class A is killing me... I had to put the book down for the last two days, and figure I would take another stab at it... the part that makes my brain freeze is 255.255.0.0. Just when I think it clicks (ie- the second octet is a 'block' of one...so when I first host is asked for--it's 10.0.0.1 then 10.1.0.1) I can't figure out why the one moved to the second octet...
But off to figure it ...

Because the 10.0.0.1 is the first host on the first subnet.

Remember, since it is a Class A network and you have your default mask set to 255.255.0.0 that means that the subnets in the 2nd octet go by 1, like you said. Here are your available subnetworks...

10.0.0.0
10.1.0.0
10.2.0.0
10.3.0.0
10.4.0.0
10.5.0.0
|
|
Down to the last one...

So on the first subnet you are allowed, 10.0.0.0, the first host would be 10.0(subnet).0.1(host)

On the second subnet, 10.1.0.0, the first host would be 10.1(subnet).0.1(host)

On the third subnet, 10.2.0.0, the first host would be 10.2(subnet).0.1(host)

And so on...

Sulblk27

Thank you markzab, I think I just got it...for some reason I was not thinking the zero was the subnet ...once I got to the zero I stopped....I am going to go do a few examples to see if it actually 'dawned' on me what I was doing wrong. Again, Thank you

deneb829

Sulblk27 wrote:

Very inspiring deneb829, I'm one of those that are barely hanging on by a thread...for some reason Class A is killing me... I had to put the book down for the last two days, and figure I would take another stab at it... the part that makes my brain freeze is 255.255.0.0. Just when I think it clicks (ie- the second octet is a 'block' of one...so when I first host is asked for--it's 10.0.0.1 then 10.1.0.1) I can't figure out why the one moved to the second octet...
But off to figure it ...

Sulblk - You need to look at it in it's binary representation. Write the ip address and subnet mask in binary. Class A, B, and C subnets don't always apply to class A, B, and C subnets. For example - it is acceptable to have a network that is 10.0.0.0 with a subnet mask of 255.255.255.0. The 255.0.0.0 is just the default subnet mask

Written in Binary:

00001010.00000000.00000000.00000000 (10.0.0.0)
11111111.11111111.11111111.00000000 (255.255.255.0)

Any part of the IP address that matches up to a 1 in the subnet field is part of the network address and any number that matches up to a 0 in the subnet field is part of the host address. So we know that on a network the network address stays the same on all of the computers and just the host portion changes to identify a single host (computer., server, printer, etc.)
10.0.0.0 = network address
10.0.0.1 - 10.0.0.254 = available for hosts
10.0.0.255 = Broadcast address
So this network can have 254 hosts because the 1st address is the network address and the last address is the broadcast address.

Now if we use the default subnet for 10.0.0.0 it looks different. We know that in decimal notation, the default subnet for a class A is 255.0.0.0

Written in Binary:
00001010.00000000.00000000.00000000 (10.0.0.0)
11111111.00000000.00000000.00000000 (255.0.0.0)

Remember - if the IP address matches up with a 1 in the subnet mask it is part of the network address and all hosts on that network must have the same network portion. Any part of the IP address that matches up with the 0's in the subnet is part of the host address. In this case it looks like this:
10.0.0.0 = network address
10.0.0.1 - 10.255.255.254 = available for hosts
10.255.255.255 = broadcast address
So this network gives us over 16,777,213 hosts on a single network. Not very a practical sized LAN. In real life, subnets this size mainly used on internet backbone routers.

Another thing to remember is when the 1's in the subnet mask stop and the zero's start, you can't go back to using 1's again. For example this would be an illegal subnet:
11111111.00000000.11111111.00000000. (255.0.255.0) bad subnet mask. Windows is nice enough to warn you about an invalid subnet. Try it sometime.

So, subnets can only be specific numbers - Here is an example of a valid subnet that doesn't adhere to a class A, B or C:

11000000.10101000.00000001.00000000 (192.168.1.0)
11111111.11111111.11111111.11111100 (255.255.255.252)

Remember again, on a network any part of the address that lines up with a 1 is part of the network address and any part that lines up with a 0 is the host address. In this case our network is REALLY small:

11000000.10101000.00000001.00000000 192.168.1.0 (network address)
11111111.11111111.11111111.11111100 255.255.255.252

11000000.10101000.00000001.00000001 192.168.1.1 (host address)
11111111.11111111.11111111.11111100 255.255.255.252

11000000.10101000.00000001.00000010 192.168.1.2 (host address)
11111111.11111111.11111111.11111100 255.255.255.252

11000000.10101000.00000001.00000011 192.168.1.3 (broadcast address)
11111111.11111111.11111111.11111100 255.255.255.252

You may have to read this a few times, but this is basically it. Hope this helps some.

*** Special Note to Subnetting Geniuses - I know this is a simplified explanation. Please fight the urge to complicate the example with too much detail ***

kafifi13

It takes a while. You just have to practice. If you have the cisco press book try doing all of those subnet practice stuff they have. I Just finished the book now i'm going to take time to do practice tests.

markzab

deneb829 wrote:

*** Special Note to Subnetting Geniuses - I know this is a simplified explanation. Please fight the urge to complicate the example with too much detail ***

Mine was the simple one.

deneb829

markzab wrote:

Mine was the simple one.

Far be it from me to argue subnetting with a CC anything.
Still, I just think subnetting makes alot more sense when you can see it in it's native Klingon ... er, I mean binary.

markzab

deneb829 wrote:

markzab wrote:

Mine was the simple one.

Far be it from me to argue subnetting with a CC anything.
Still, I just think subnetting makes alot more sense when you can see it in it's native Klingon ... er, I mean binary.

I'm actually not a CC-anything. I wasn't arguing with you at all. I just found it funny that you made that comment after all the binary which can make ones eyes cross online. :P

mikej412

mobri09 wrote:

Does anyone just love to subnet?

The chapter won't last forever.... no matter how slow you read.

You can get your subnetting fix at www.subnettingquestions.com

But remember, IPv6 is coming

NightShade1

At what year you think mike IPV6 will replace IPV4?

DirtySouth

I wouldn't go so far as to say I love subnetting, but I don't mind doing it at all.

deneb829

markzab wrote:

I'm actually not a CC-anything. I wasn't arguing with you at all. I just found it funny that you made that comment after all the binary which can make ones eyes cross online. :P

OMG! You mean when your certifications expire you forget everything at that moment!?

I guess I understand. Binary is just a beautiful thing to me, so I don't mind looking at long strings of 1's and 0's.

Sulblk27

Thank you deneb829, working it out in binary was the next step...your explanation will be a reference to me as I go along with practice questions tonight. I believe once I remember the bits that are used (ie /9 thru /30) and apply the binary (which for some reason I really don't mind at all ) The class A ( /16 )will finally sink in. I truly do appreciate the assistance from all....not going forward until I get subnetting down 'in my head'

deneb829

Sulblk27 wrote:

Thank you deneb829, working it out in binary was the next step...your explanation will be a reference to me as I go along with practice questions tonight. I believe once I remember the bits that are used (ie /9 thru /30) and apply the binary (which for some reason I really don't mind at all ) The class A ( /16 )will finally sink in. I truly do appreciate the assistance from all....not going forward until I get subnetting down 'in my head'

I wish you luck, you'll definitely get it because you want to understand it. Just stick with it.

The class A subnet is actually a /8. To get the slash number, just write the subnet out in binary and count the number of 1's.

Class A = /8
11111111.00000000.00000000.00000000 (255.0.0.0)

Class B = /16
11111111.11111111.00000000.00000000 (255.255.0.0)

Class C = /24
11111111.11111111.11111111.00000000 (255.255.255.0)

markzab

deneb829 wrote:

markzab wrote:

I'm actually not a CC-anything. I wasn't arguing with you at all. I just found it funny that you made that comment after all the binary which can make ones eyes cross online. :P

OMG! You mean when your certifications expire you forget everything at that moment!?

I guess I understand. Binary is just a beautiful thing to me, so I don't mind looking at long strings of 1's and 0's.

Yes, correct. Have you ever seen the movie Men in Black? Remember the memory wiping device with the red flash? Once your cert expires a Cisco van pulls up and 3 men jump out, tackle you, and flash you. Poof, cisco memory gone.

Sulblk27

My apologies...In the example I have, this may be what is confusing me... it has 255.255.0.0 /16...stating "The 255.255.0.0 mask with a Class A address is using 8 subnet bits." So I assume it is referring to octet 2 2^8= 256 subnets and 2^16 - 2 = 65,534. So when I see subnet 10.0.0.0 First host 10.0.0.1---for some reason I understood that, but the next subnet is 10.1.0.0 first host 10.1.0.1-- it took me into a tail spin..... wait I believe I just figured out my mistake...(as I am reading the exercise)

I have been looking at the first subnet, first host...and failing to go to the last host 10.0255.254...(in this example)
I 'skipped over to the next subnet 10.0.0.0, first host 10.1.0.1...confusing the two subnets... ...
OK....I will take my eyes away from the sun, and try this with some sense about me...

deneb829---thank you so much for your help..and encouragement...reading the post made me see things in a different light....( I have taken notes )

mobri09

I would of never have guessed every loves to subnet so much like I.
www.subnettingquestions.com is awesome.
I need to subnet faster though

deneb829

mobri09 wrote:

I would of never have guessed every loves to subnet so much like I.
www.subnettingquestions.com is awesome.
I need to subnet faster though

You really should listen to John Denver too!

Actually, I am glad to hear that someone else loves to subnet. I was so inspired by today's posts that I actually taught subnetting this afternoon in my Operating Systems class. I was surprised how much the students paid attention. I think I was glowing with my love for subnetting ... plus I bribed them with beaucoup extra credit points on their exam next week if the learned it. They seemed to have grasped it for the most part, I guess we'll see next week.

mobri09

Glad to hear this post inspired you. One of my coworkers in the network department cannot stress subnetting enough. Its the building blocks baby...the building blocks