Solved

IP address Classes

Posted on 2014-10-02
21
426 Views
Last Modified: 2014-10-13
I am trying to understand IP address classes , I checked the link below:
http://vlsm-calc.net/ipclasses.php

I am not sure why the top part is saying class C subnet mask is 255.255.255.0 and below Private IP address table it is showing it 255.255.0.0, the same for class B the top part is showing 255.255.0.0 and the Private table is showing 255.240.0.0

Another thing that also confuses me is the Number of the Networks. for instance Class C that has subnet mask 255.255.255.0. How many Networks and hosts we can have.???
To my understanding if we have 192.168.1.X 255.255.255.0 , it means we have on Network since the first 3 octets will not change , but will have (2^8)-2=254 Hosts...

Any explanation will be very much appreciated..

Thanks
0
Comment
Question by:jskfan
  • 9
  • 7
  • 2
  • +3
21 Comments
 
LVL 13

Assisted Solution

by:frankhelk
frankhelk earned 72 total points
ID: 40356636
OK - I'll try ... there's a difference between regular (public) address spaces and private (non-public) networks.

In terms of a public network, the classes A,B and C decribe usual sizes of networks, while the classes D and E describe address ranges that are public visible but not usable for regular host addresses (class D is reserved for multicast use and is to be handled especially in routers and switches, while class E is reserved for experimental use).

Besides of the common sizes of the classes A,B and C, it is theoretical possible to use any mask length from (theoretical) 1 leading bit (128.0.0.0) to 23 leading bits (255.255.255.254) based on the needed number of client addresses in the net. I've seen several examples, like a 255.255.240.0 mask.

The private address ranges A (10.0.0.0/8 =10.0.0.0 ... 10.255.255.255) B (172.16.0.0/12 = 172.16.0.0 ... 172.31.255.255) and C (192.168.0.0/16=192.168.0.0 ... 192.168.255.255) have a special meaning. They're reserved for networks behind a NAT router and are never routed into the internet. That way they can be used virtually infinite times w/o address collisions, because the clients are masked behind the router's address. It's a way to expand the narrow IP4 address space for the ever growing needs of the internet, where every coffe machine and coke machine need teir own IP address. IPV6 is the answert to the fact that even that is not enough ... ;-S

To name both things in the same manner is indeed a bit confusing ....

P.S.: The number of theoretical network classes is limited to 32, because the definition of a network mask allows only a uninterrupted stream of 1s from the start of the mask.
255.255.240.0 = 11111111.11111111.11110000.00000000 is allowed
240.255.240.0 = 11110000.11111111.11110000.00000000 is forbidden

Open in new window

0
 
LVL 50

Assisted Solution

by:Don Johnston
Don Johnston earned 357 total points
ID: 40356707
I am not sure why the top part is saying class C subnet mask is 255.255.255.0 and below Private IP address table it is showing it 255.255.0.0, the same for class B the top part is showing 255.255.0.0 and the Private table is showing 255.240.0.0
That's an interesting (and confusing) way of showing the addresses. :-)
While you could use the 255.240.0.0 mask for the class B private address, you probably wouldn't.

It's simply that there are a number of class B (and class C) private addresses and if you wanted to use them as a single contiguous range, that's the mask you would use. But in reality, if you needed more addresses than a class B would provide, you would use a class A address.

Another thing that also confuses me is the Number of the Networks. for instance Class C that has subnet mask 255.255.255.0. How many Networks and hosts we can have.???
To my understanding if we have 192.168.1.X 255.255.255.0 , it means we have on Network since the first 3 octets will not change , but will have (2^8)-2=254 Hosts...

Your view is (in my viewpoint) technically correct. The chart is showing the maximum number of possible subnets if you were to extend the mask.
0
 
LVL 10

Assisted Solution

by:t_hungate
t_hungate earned 71 total points
ID: 40356754
I think it is good to all the way back to the basics if you are having issues with understanding networking or sub-netting.  That means seeing the problem in its native form and then translating it, so start in binary, and then move it to decimal to see what is really happening and why there are XX number of hosts to each node.

There is a somewhat straight forward article here: http://www.networkcomputing.com/netdesign/ip101b.html

I attached an image that helps to visualize the binary conversion of the IPv4 address (courtesy of hitech.net)

Hopefully it is helpful.
0
 

Author Comment

by:jskfan
ID: 40357376
The chart is showing the maximum number of possible subnets if you were to extend the mask.

 If I understand:
192.168.1.X 255.255.255.0, I have one subnet and 254 hosts from 192.168.1.1 to 192.168.1.254
if I need to have 512 hosts I will have to take one Bit from Network portions , correct ? if so how will I change the 192.168.1.x ??
0
 
LVL 50

Assisted Solution

by:Don Johnston
Don Johnston earned 357 total points
ID: 40357415
No, not quite.

192.168.1.0/24 is a network which can have 254 hosts.

If you need to have 512 hosts, then you would (typically) take a class B and subnet it.

172.16.0.0/22 would give you a subnet that could accomodate 1022 hosts.

But... because there are 256 contiguous class C addresses, you could supernet some of those. (subnetting is where you increase the length of the mask and supernetting is where you decrease the length of the mask)

For example 192.168.0.0/22 would also give you 1022 hosts.

If you had tried either of these examples with a 23 bit mask, you would only be able to have 510 hosts.
0
 

Author Comment

by:jskfan
ID: 40357596
If you had tried either of these examples with a 23 bit mask, you would only be able to have 510 hosts.

OK... Let' say I need 510 hosts when initially having 192.168.1.0/24 Network
How is the Network going to be changed ?
0
 
LVL 50

Assisted Solution

by:Don Johnston
Don Johnston earned 357 total points
ID: 40357616
Well, you're not going to do it if you're starting with 192.168.1.0/24.

If you were starting with 192.168.0.0/24, all you would do is change the mask to a /23. Then you would have 510 hosts (192.168.0.0 - 192.168.1.254).

Or you could start with 192.168.2.0 with a /23 mask. That would give you 192.168.2.0 - 192.168.3.254.
0
 

Author Comment

by:jskfan
ID: 40358550
OK...let's say we start with 192.168.0.0/23
In Binary
11111111.11111111.11111110.00000000.


how are Hosts going to be positioned on the subnets...?
for instance:

First subnet :
first host will be 192.168.0.1 and the last will be 192.168.0.254
Second Subnet:
First host will be 192.168.1.1 and the last will be 192.168.1.254

It still 254 host per subnet(508 Total), and Only 2 subnets
0
 
LVL 50

Assisted Solution

by:Don Johnston
Don Johnston earned 357 total points
ID: 40358560
Read my previous post.

192.168.0.0/23 will yield 510 host addresses.

192.168.0.1 - 192.168.1.254
0
 

Author Comment

by:jskfan
ID: 40358603
192.168.0.0/23  = 192.168.0.0 255.255.254.0

255.255.254.0=      11111111.11111111.11111110.00000000
Number of hosts= 00000000.00000000.00000001.11111111 which gives (2^9)-2=510


I do not see how you came up with:
 192.168.0.1 - 192.168.1.254
0
How your wiki can always stay up-to-date

Quip doubles as a “living” wiki and a project management tool that evolves with your organization. As you finish projects in Quip, the work remains, easily accessible to all team members, new and old.
- Increase transparency
- Onboard new hires faster
- Access from mobile/offline

 

Author Comment

by:jskfan
ID: 40358685
On the third octet 255.255.254.0, it will give us 2 subnets , so it will be 192.168.0.0 and 192.168.2.0 , 192.168.1.0 should be a Broadcast...
0
 

Author Comment

by:jskfan
ID: 40358687
192.168.1.0 should be a Broadcast...
192.168.1.255 should be a Broadcast...
0
 

Author Comment

by:jskfan
ID: 40358866
I guess  got this part:
256-254=2 , means first Network is 192.168.0.0 and the next will be 192.168.2.0 and The broadcast will be 192.168.1.255

The other part ?? I am trying to figure out 510 hosts ??
can  192.168.0.255 be a host?
can 192.168.1.0 be a host ?
If so then the 2 subnets will have hosts from 192.168.0.1 to 192.168.0.255 (255 hosts) and from 192.168.1.0 to 192.168.1.255 (255 hosts) , that will make 255+255=510
0
 
LVL 50

Accepted Solution

by:
Don Johnston earned 357 total points
ID: 40358910
256-254=2 , means first Network is 192.168.0.0 and the next will be 192.168.2.0 and The broadcast will be 192.168.1.255
There are not two subnets.  There is one supernet. Or one network if you want to use that term. The significant point is there is only one.
can  192.168.0.255 be a host?
can 192.168.1.0 be a host ?
0.255 is a host as is 1.0.
If so then the 2 subnets will have hosts from 192.168.0.1 to 192.168.0.255 (255 hosts) and from 192.168.1.0 to 192.168.1.255 (255 hosts) , that will make 255+255=510

You are still thinking classfull.  The only thing that matters is the mask. Having a 9-bit host field gives you 510 hosts.
0
 

Author Closing Comment

by:jskfan
ID: 40359598
I will do some reading and practice and come back...
Thanks
0
 
LVL 25

Expert Comment

by:Fred Marshall
ID: 40360144
It's not clear to me why folks continue to learn about "classes".  The whole idea is archaic and unnecessary.

I didn't see any real comments in this regard.  Don Johnson said "You are still thinking classfull" which comes closest to making this point.

So, starting at the beginning, learn about subnetting (which I think you have gotten well into by now) and then, if you MUST, "back into" classes for the purposes of academic study.  It will be much clearer to you that way I believe.
0
 
LVL 50

Expert Comment

by:Don Johnston
ID: 40360171
It's not clear to me why folks continue to learn about "classes".  The whole idea is archaic and unnecessary.
Because whether you like it or not, it's still taught and tested.  If you're looking at any network training or certification, they still use the concept.
0
 
LVL 25

Expert Comment

by:Fred Marshall
ID: 40360350
I'm sorry, I should have been clearer:
It's not clear to me why folks continue to teach about "classes".
A suggestion might be that they should also teach germanium transistor technology just to be consistent!  :-)

My recommendation, as others have made, is to learn about subnetting from the subnet mask up and, when time allows or demands, THEN learn about the buggy whips called "classes".
0
 
LVL 50

Expert Comment

by:Don Johnston
ID: 40360392
Good luck with that.
0
 

Author Comment

by:jskfan
ID: 40360394
Thank you Guys.... This tool is much more detailed about subnet and supernet:
http://jodies.de/ipcalc?host=192.168.0.0&mask1=24&mask2=25
0
 

Expert Comment

by:Carlos Velez
ID: 40379160
That last website has a lot of information; you can try this one also http://www.cronos.est.pr/tcpip/
0

Featured Post

How your wiki can always stay up-to-date

Quip doubles as a “living” wiki and a project management tool that evolves with your organization. As you finish projects in Quip, the work remains, easily accessible to all team members, new and old.
- Increase transparency
- Onboard new hires faster
- Access from mobile/offline

Join & Write a Comment

This article is a guide to configure bridging on Cisco Routers.  This is something I never knew was possible until after making a few phone calls to Cisco.  Using bridging saved our company money by not requiring us to purchase a new switch.  Bridgi…
I have seen some questions on problems with SSH/telnet access to Cisco routers that may occur despite the fact that from a PC connected to your LAN, Internet connectivity is in place and users can access Internet sites without any issues.  There are…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…

759 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

19 Experts available now in Live!

Get 1:1 Help Now