Subnet

CrackerJacker1

Daemon Poster
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987
Location
USA
IP4 and Subnet questions


My IP address 153.0.00.0 range and under local area connection status it is showing my Subnet mask is 255.255.255.0
Well I'm not sure what I'm asking really. It just seems like it should be 255.255.0.0 (According to the picture above)
Can you look at a IP and just know what a subnet would be.


I'm still not sure what the heck a subnet mask really does and what the purpose is. If your IP address is going what your given by the ISP or what your assigning for your internal IP. The subnet is just going based off what your IP address and there wouldn't be multiple outcomes of what your Subnet mask could be.




Also, since your here... I'm reading subnetting does not increase the number of IP addresses available. It increases the number of network IDs and, decreases the number of node IDs per network.
To be honest I'm really confused. What the heck do the mean by network. Network IDS. Nodes ID?
Obviously I know what a general network is.


Network ID would be using your internal IP (I think). According to the picture below Class C range. 192(Root).168(Network).1(Network).1(The computer/router I'm using). So NETWORK ID: 1 192.168.1.1. NETWORK ID: 2 192.168.2.1




Node ID: To be honest I have no Idea what a Node is.




Sorry guys. I should probably look at all these things individually and fully understand them piece by piece. I've been drinking monsters all day so my mind is racing.
 
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crazyman143

Fully Optimized
Messages
2,965
An ip address can be broken into two parts. the first part identifies a network, and the second part identifies a specific computer on that network.

The computer needs the subnet mask to differentiate between the two parts. It needs to know where the network part (network ID) ends, and where the numbers for the computers, or hosts, begins.

so if you have this:

192.168.1.120
255.255.255.0

well the computer will break this down to binary, which looks like this:

11000000.10101000.00000001.01111000
11111111.11111111.11111111.00000000

The 1's in the subnet mask mean this is network portion, the 0's mean this is hosts portion. Now the computer knows that all the bits in the first 3 sections (octects) of the IP address are identifying the network ID. the last section, which is 120 in this case, is identifying this computer or host.

If the subnet masks were not the same for all computers on a local network, they wouldn't be able to communicate, because they would all have different information, and they'd think they were all on other networks.

Another example:

172.16.0.120
255.255.0.0

in binary:
10101100.10101100.00000000.01111000
11111111.11111111.00000000.00000000

now in this case, the network portion is the first 2 octets. (172.16)
any any numbers in the last two octets could be other hosts on that network. So,

172.16.0.100
172.16.20.100

both of those could be other computers (or hosts) on this network. The computer knows this by the subnet mask.

I hope that makes a little sense. It's a confusing subject. I could go into more detail of how you can use the mask to "save" ip addresses, and how the binary conversion works.
 
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