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? Adam 
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 
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? Adam 
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.
Take class of address: First octet rule  0127 Class A Default Netmask 255.0.0.0 128171 Class B Default Netmask 255.255.0.0 127223 Class C Default Netmask 255.255.255.0 Number of bits subnetted: IPADDR=10.0.0.0 NETMASK=255.255.0.0 Default netmask since the IPADDR starts with 10 would be 255.0.0.0 Therefore, you borrowed 8 bits to get the 255.255.0.0. 2^8 = 256 subnets possible 
Thanks again
Hey this second reply was a little less straigt forward for me but I am off to Read up on RFC1519!!
So impressed by your reply I have printed out this topic! Thanks Adam 
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Hi, There are 2 different approach in IP adressing i think. One says that B Class is between 128191 and other is as u say 128171. Which one is right? 
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0xxxxxxx Class 'B' networks are 128191 in the first octet defined bitwise: 10xxxxxx Class 'C' networks are 192223 in the first octet defined bitwise: 110xxxxx Therefore, it must be this way. No other scheme. Cheers, Justin 
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Well actually i agree with this one already but; Quote:
Thanx again 
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