IP and Subnetmask

IP and SubnetmaskAs you know, Fajar has been post about IPv6 vs IPv4 and now i’ll discuss more detail about IP espescially about IPv4.

IP stand for Internet Protocol. IP is something we can see as address of device like computer, switch, router, etc. IP is used for communication beetwen 2 device or more in network or if the device were handphone, IP would be a phone number.

IP addres is consist of 4 block binary number and each block can be filled from 0 to 255, for example:

IP always have a couple called subnetmask. Subnetmask also have 4 block binary number like IP, but subnetmask have a diffrent function.

Subnetmask have function to determined IP to the corresponding network. Subnetmask ussually used when we do routing or transferring data where the device (router or computer) will check if IP destination are in the same network.

If the network are same, message/data will directly sent to computer destination, because the computer sender and coumputer destination have to in the same network. If the network are different the message will sent to exit door (ussully called default gateway) in order to be forwarded to the destination network.

As i said before subnetmask also have 4 block binary number and that block also can be filled 255 to 0, example or

How to see network from an IP is doing function mathematical function AND through IP and subnetmask.

For example we have 2 computer with IP A & B:

A :

B :

If both of them use subnetmask, so the result of AND function wiil show network from computer A & B as follow: AND = AND =

From result above we can see that computer A is from network and computer B is from network, that means A & B is from diffrent network, so it’s impossible to creat a communiation without other device. To help this computer we can use intermediate device  tool that called default gateway or router.

If the computer use subnetmask, so the AND result will show as follow: AND = AND =

from this result we can se that computer A and computer B is from same network if we use this method we don’t need intermediate device because the network has the same.

Destination IP is devide to 2 groups there itself and foreign group. To be able to ‘talk’ with outside groups that needed bridging device or a gateway in order to ‘get out’. That gateway ussually called default gateway or default router

Default gateway ussually seves as bridge beetwen lokal network and non-lokal network, Its function is similar to the way a letter postman. For example we want to send letter from jakarta to surabaya, we just need to send that letter to the postman. But that postman will never send the letter by himself, that letter will sent to another postman until postman in surabaya receive it and then postman in surabaya send it to the destination. How router is same, forward our message to the next router, and then forward again, again, and again until the message arrive at our router network and finally the message will sent to our computer.


Muhammad Wildan – 125150300111033


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