# what is the difference between net ID and host ID??



## iinfi (Jul 17, 2005)

what is the difference between net ID and host ID??
in a class C IP address say, 192.52.56.8 the first 3 octets denote the net ID while the last octet shows the host ID. what are the 2 used for ?

again in a class B IP address say, 172.52.36.5 the first 2 octets show the net ID while the last 2 denote the host ID.... what is the significance of the netID and hostID???

i got this definition for host ID frm google search, but i still didn't understand ...


> An identifier for a host. A host ID uniquely identifies a host within an address family on a network but does not identify the network. A host ID is not necessarily sufficient to establish communications with a host.



plz HELP ....
thanks ....


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## digen (Jul 17, 2005)

Its very simple mate.The network id is the id of the network & resembles the network.The host id is the identification of the host in the network.

Class A:Network.Node.Node.Node
Class B:Network.Network.Node.Node
Class C:Network.Network.Network.Node

The above is the way upon which its classified depending upon which Class the IP address belongs to.

If there is a network with a number of subnetted networks.How will a packet arriving at the default gateway/router determine where it should go?
It all comes down to the "network id"[net id] portion which makes it possible to locate the network.The packet would then traverse its way through a switch/hub to the appropriate host with the help of the host id.
Always remember routers dont care about hosts,all they care about is segmented networks.
I hope this helps.


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## iinfi (Jul 17, 2005)

thanks for your reply ...


> Class A:Network.Node.Node.Node
> Class B:Network.Network.Node.Node
> Class C:Network.Network.Network.Node



i had seen this in my book also ..... 
class A supports *16,777,216* hosts per network ..
class B supports        *16,384* hosts per network .
class C *256*  .... 

now how do u arrive at these figures (in bold .)...?


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## digen (Jul 17, 2005)

Hmm although I suck when it comes to math I will try my level best here   

As i've already explained Class A is Network.Node.Node.Node

Now what is a IP address? Its a 32 it[4 byte] long address.
What does this mean?Each byte is equal to 8 bits.
Thus how many node addresses can the Class A address have?
2^24 [i.e 2 raise to the power 24]Why because the first byte makes the network id,the rest three bytes make the host id which equals to 24bits.So you want to find the hosts aint it?
2^24=16,777,216
You may ask why 2 raise to n? Simple because a bit is either a 1 or a 0.

Similarly just follow the network classes classification for Class B & Class C & you will finally end at those numbers without any confusion.


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## iinfi (Jul 17, 2005)

hi network guru
thanks for your help ..... will trouble u if i have any further confusion...


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