Solved: finding the network address from a regular IP adress

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Dropped_2_C

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Apr 28, 2009
Messages
18
Ok I need help, I have found the Subnet, the Broadcast address, and class.

For example let's take address 10.17.231.88, I know the class is A because the range the first set of numbers is in, the Subnet is 255.0.0.0, or in this case this is the default, and lastly the broadcast is 10.255.255.255.

Am I overlooking the obvious? I mean the broadcast for a class B would be with the IP 147.212.16.0 would be 147.212.255.255

Why am I lost I mean what gives am i not understanding the network address


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Joined
Dec 27, 2008
Messages
33
Just use the ANDing process.

You take your IP address and the Subnet mask and turn them into binary.

So for the address 147.212.16.0/16 you would do the following:

147.212.16.0 =
10010011.11010100.00010000.00000000

255.255.0.0 =
11111111.11111111.00000000.00000000

Then you simply compare each number in the IP address to the one below it. If they are both 1, then you put a 1 for the network address. If they are anything else, you put a 0. So like this:
10010011.11010100.00010000.00000000
11111111.11111111.00000000.00000000
10010011.11010100.00000000.00000000


So that means that your network address would be 10010011.11010100.00000000.00000000, which in decimal format is:
147.212.0.0
 

TerryNet

Terry
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Mar 23, 2005
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In any subnet, or range of IP addresses, the Network address is the lowest possible and the Broadcast is the highest possible.
 

Dropped_2_C

Thread Starter
Joined
Apr 28, 2009
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thanks guys that helps the lowest possible and the highest possible makes sense and is easy to remember
 
Joined
Dec 27, 2008
Messages
33
thanks guys that helps the lowest possible and the highest possible makes sense and is easy to remember
Be careful though, when you start getting into variable length subnetting determining the network address isn't as easy as just putting the lowest number as 0.

The easiest way to do it is to look at the subnet mask, if it's /8, /16, or /24 then you know that the network address will be a 0. So like 10.81.7.233/16's network address would be 10.81.0.0 and it's easy to remember.

But if you had an address with like 172.16.100.100/26, then you would have to use the ANDing process that I showed you earlier because the network address would not end up having a 0, it would be higher.
 
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