Solved

Network Address Range - CIDR Notation - Explaination Please?

Posted on 2006-06-12
12
1,343 Views
Last Modified: 2007-12-19
Hello All;

  We are fixing to correct a lot of bad Entries from our SMTP BLOCK LIST in our Mail Server.
The following information we are needing to find out.
===========================================================
IP Address
172.16.0.0 - 172.31.255.255  /12

If I was to enter the:   172.16.0.0        into our IP Field. And then Enter   172.31.255.255   into our MASK field.
Would that mean that it will look at and BLOCK out everything from    172.16.0.0 - 172.31.255.255

I am understanding that correctly?

10.0.0.0 - 10.255.255.255 /8   --> I add this in, and it BLOCKS everything in that range.
172.16.0.0 - 172.31.255.255 /12  --> This I am not sure about?
192.168.0.0 - 192.168.255.255 /16  --> This block everything in that range

Thanks all;
Carrzkiss
0
Comment
Question by:Wayne Barron
12 Comments
 
LVL 15

Expert Comment

by:Ryan_R
ID: 16889942
The CIDR Notation is basically the xxx.xxx.xxx.xxx format that you are already using to enter in your IP addresses with the /xx suffix.

The following link should help you (from Wikipedia):
http://en.wikipedia.org/wiki/Subnetwork

I sincerly hope you understand it (even I had to read it more than once)

Ryan
0
 
LVL 76

Expert Comment

by:arnold
ID: 16889953
no.

The CIDR notation translation is to take 8 out of the number.
Every time you take an 8 out the netmask
Netmask   = CIDR notation
255.0.0.0 = /8
255.255.0.0 = /16
255.255.255.0 = /24
255.255.255.255 = /32


/12 take out one 8
the remaining 4 = 128+64+32+16
255.240.0.0 = /12


0
 
LVL 30

Author Comment

by:Wayne Barron
ID: 16889979
Ryan - I had already read the information on that site, and got some good information
But nothing that would explain in detail on what I am doing here.
----------
Arnold - Thanks for the information that you have provided, though it still does not tell me
What I was asking, I think you was just replying to what 'Ryan' had stated in his post.

---------
Once again:
If I add in

IP Address            Subnet Mask
172.16.0.0          172.31.255.255

Would that cover everything from
172.16 - 172.31.255.255
In the BLOCK list?
0
 
LVL 79

Expert Comment

by:lrmoore
ID: 16890026
>And then Enter   172.31.255.255   into our MASK field.
>Would that mean that it will look at and BLOCK out everything from    

No. 172.31.255.255 is a broadcast address, it is not a mask. You need a real mask, ie..

IP address 172.16.0.0  MASK 255.224.0.0
CIDR notation: 172.16.0.0/12
Would result in blocking all hosts in range 172.16.0.1 - 172.31.255.254

0
 
LVL 30

Author Comment

by:Wayne Barron
ID: 16890109
Thank you lrmoore (And nice to see you again, been a while since we have crossed paths)
OK, so that would block everything if the subnet is:  255.224.0.0

Would that mean that this:

10.0.0.0 - 10.255.255.255    subnet: 255.255.255.255
Would that block everything from  10.0.0.0 ?

I have been admining our network here for years, and there is still a lot that I need to learn about it all.

Les say that you have the following Range of IP Address's

192.64.0.0   192.95.0.0
(&)
192.56.0.0 - 192.57.0.0
Would the bottom one be just
192.56.0.0    255.255.0.0
192.57.0.0    255.255.0.0

Thanks lrmoore for all the information that you can possibly provide me with on this.
0
 
LVL 79

Expert Comment

by:lrmoore
ID: 16890235
>10.0.0.0 - 10.255.255.255    subnet: 255.255.255.255
Would that block everything from  10.0.0.0 ?

Nope. that mask would block only 10.0.0.0
10.0.0.1 would get throuth
On the other hand,
10.0.0.0 - 10.255.255.255  subnet = 255.0.0.0
That would include the complete range

For 192.56.0.0 - 192.57.255.254 you can use one entry with mask 255.254.0.0
 192.56.0.0 / 15

0
6 Surprising Benefits of Threat Intelligence

All sorts of threat intelligence is available on the web. Intelligence you can learn from, and use to anticipate and prepare for future attacks.

 
LVL 30

Author Comment

by:Wayne Barron
ID: 16890296
This is enough to drive someone nuts :)

lrmoore
Do you perhaps have a link that has/shows different IP Ranges that shows all this information on it?
This would make it a lot easier for myself and others to go to for information.
As, right now, I am totally lost, I am trying to follow, beleive me, but I am getting lost.

Because right now, we have 100's of entries in our BLOCK list, and are similuar to
192.56.0.0    255.255.0.0
192.57.0.0    255.255.0.0
&
192.64.0.0   192.95.0.0
& on & on.

Thanks
0
 
LVL 79

Accepted Solution

by:
lrmoore earned 125 total points
ID: 16890734
You  might just want to get an IP subnet calculator
http://lantricks.com/lancalculator/
Easier to just work with the calculator than try to understand it all.
Took me a loooonnnnnggggg time to understand that subnet mask is nothing more than a binary string of 1's ... where the 1's stop, that determines the network ID and where the 0's start determines the host ID

255.0.0.0 = 11111111.00000000.00000000.00000000
255.255.0.0 = 11111111.11111111.00000000.00000000
255.255.255.0 = 11111111.11111111.11111111.00000000

255.255.254.0 = 11111111.11111111.11111110.00000000
<etc>

http://www.learntosubnet.com/

0
 
LVL 30

Author Comment

by:Wayne Barron
ID: 16890809
That will do it.
Thanks once again for your helpful advice & information Mr. lrmoore;

Wayne
0
 
LVL 30

Author Comment

by:Wayne Barron
ID: 16890890
lrmoore;
1 quick question, to make sure that I am going to do this correctly.

The following IP Address:
192.168.192/18

Wold the Subnet be:  255.255.192.0  ?

I am believing that is correct.
In the [LanCalculator] For the [Subnet Mask Info]
It list:
Class        Mask                Inv. Mask             Num Hosts           Prefix
C          255.255.192.0     0.0.63.255            16382                   /18

So, it looks like the correct MASK for the IP Address Range of:
192.168.192/18
Would be:  255.255.192.0

-------------
Also, in the list I just made above. The    
 Num Hosts   -  Is the the Number of IP Address in the  /18 ?

Thanks a bunch.
Wayne
0
 
LVL 79

Expert Comment

by:lrmoore
ID: 16890899
You got it!
Gets easier with a calculator, doesn't it?
0
 
LVL 30

Author Comment

by:Wayne Barron
ID: 16890913
Thank you much buddy.
That little program is cool, it is really cool that the developer was nice enough to give it away for free. :)

Take Care and thank you once again, especially for the Calculator.

Wayne
0

Featured Post

What Should I Do With This Threat Intelligence?

Are you wondering if you actually need threat intelligence? The answer is yes. We explain the basics for creating useful threat intelligence.

Join & Write a Comment

If your business is like most, chances are you still need to maintain a fax infrastructure for your staff. It’s hard to believe that a communication technology that was thriving in the mid-80s could still be an essential part of your team’s modern I…
Meet the world's only “Transparent Cloud™” from Superb Internet Corporation. Now, you can experience firsthand a cloud platform that consistently outperforms Amazon Web Services (AWS), IBM’s Softlayer, and Microsoft’s Azure when it comes to CPU and …
This video gives you a great overview about bandwidth monitoring with SNMP and WMI with our network monitoring solution PRTG Network Monitor (https://www.paessler.com/prtg). If you're looking for how to monitor bandwidth using netflow or packet s…
In this tutorial you'll learn about bandwidth monitoring with flows and packet sniffing with our network monitoring solution PRTG Network Monitor (https://www.paessler.com/prtg). If you're interested in additional methods for monitoring bandwidt…

744 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

8 Experts available now in Live!

Get 1:1 Help Now