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 jimdaworm 11-16-2003 01:38 PM

Is there freeware Network Simulation software?

I was wondering if there is some sort of a freeware program to help with learning about networks... I have seen such programs for electronic circuits but couldnīt find anything. I am having problems understanding exactly how to use subnet masks and then calculate how many hosts you could have with the mask even though I have read quite a few articles which are supposed to explain it.

Any Ideas?

 jcookeman 11-16-2003 01:46 PM

There are IP calculators...just google ip calc and you will find tons of them.

If you want to know how many hosts you can have with a given netmask then take the count the number of bit positions with corresponding zeros represented by 'n', raise two to that number and subtract '2':

255.255.255.224
=
11111111.11111111.11111111.11100000 (five zeros)
=
2^5 - 2 (raise 2 to the number of zeros - 2)
=
32 - 2
=
30

 jimdaworm 11-16-2003 02:01 PM

THANKS A LOT

Thanks for that wicked explaination I have read lots of things similar but your explaination was what I need to understand how to calculate it easily!

Subtract 2 because the the last is the broardcast address??? and I canīt remember what they first number would be??

Do you have a similar explaination for number of Physical Segments?

 jcookeman 11-16-2003 02:40 PM

To do the number of networks it is the exact opposite. Instead of using the number of zeros you use the number of ones. And you don't subtract two, but that depends on if you are doing classfull or classless ip addressing. I will use classless since that is what everyone uses nowadays. Read up on RFC1519.

First octet rule -
0-127 Class A Default Netmask 255.0.0.0
128-171 Class B Default Netmask 255.255.0.0
127-223 Class C Default Netmask 255.255.255.0

Number of bits subnetted:

Therefore, you borrowed 8 bits to get the 255.255.0.0.

2^8 =
256 subnets possible

 jimdaworm 11-18-2003 03:02 PM

Thanks again

Hey this second reply was a little less straigt forward for me but I am off to Read up on RFC1519!!

Thanks

 rapatista 10-19-2006 01:36 AM

Quote:

Hi,

There are 2 different approach in IP adressing i think. One says that B Class is between 128-191 and other is as u say 128-171. Which one is right?

 jcookeman 10-19-2006 03:53 AM

Quote:
 Originally Posted by rapatista Hi, There are 2 different approach in IP adressing i think. One says that B Class is between 128-191 and other is as u say 128-171. Which one is right?
Class 'A' networks are 0-127 in the first octet defined bitwise:

0xxxxxxx

Class 'B' networks are 128-191 in the first octet defined bitwise:

10xxxxxx

Class 'C' networks are 192-223 in the first octet defined bitwise:

110xxxxx

Therefore, it must be this way. No other scheme.

Cheers,

Justin

 rapatista 10-20-2006 07:44 AM

Quote:
 Originally Posted by jcookeman Class 'A' networks are 0-127 in the first octet defined bitwise: 0xxxxxxx Class 'B' networks are 128-191 in the first octet defined bitwise: 10xxxxxx Class 'C' networks are 192-223 in the first octet defined bitwise: 110xxxxx Therefore, it must be this way. No other scheme. Cheers, Justin

Well actually i agree with this one already but;

Quote:
u say "128-171 Class B" i didnt understand this one. Also i found this spesification in some other sources (very few). What is the point of this spesification?

Thanx again

 jcookeman 10-20-2006 08:06 AM

Quote:
 Originally Posted by rapatista Well actually i agree with this one already but; u say "128-171 Class B" i didnt understand this one. Also i found this spesification in some other sources (very few). What is the point of this spesification? Thanx again
I was drunk when I posted that. Obviously, I made a typo, but I don't remember as it was quite long ago.

 Bitbeisser 04-18-2016 04:23 PM

Quote:
 Originally Posted by jimdaworm (Post 603068) Subtract 2 because the the last is the broardcast address??? and I canīt remember what they first number would be??
In each subnet, there are two reserved and fixed IP addresses:
- the lowest IP address (all host bits are 0 (zero)) is the network address