Router AND-ing between IP address and Network Mask

AND-ing calculation

For the AND-ing operation, it is important to know this table shown below. To make it clearer, see Figure6.

Figure 6.

How to get a network address by doing surgery AND-ing on the router

Figure6 presents the results of AND-ing operations performed by the the device (router) to find out the network it belongs to a certain IP address.
We see that the IP address, belongs to the network, we received surgery AND-ing.

Router compares bits (see vertical) in each octet (byte) between IP addresses and Network mask (both have four octets).
After comparing (performing the AND-ing operation) is the result of the will and writes it.
Finally, when a device (router) converts all the bits in decimal numbers have a track that gives a particular network ie. The IP address of the network (which the respective IP address relative to the mask next to it)

And finally, why is AND-in  important

It is important when one network is divided into multiple Sub-Networks (performing subnetting).

You've probably seen in many cases an IP address instead of the network mask, a CIDR  slash format / XX, where XX can mean one of the numbers 9-31, which again depends on which class belongs to a certain IP address.
I will be based on the IP address that I mentioned and belongs to the class C private range.

So if you see an IP address that is the type /28
means that there is no default network mask (Classfull) already has subnet mask (Classeless).

About Classeless Subnet Masks will later. For now it is enough to realize that a slash (/??) writing format mask is not the same as the default network mask.
However, you could write /24 but about that on this, it is not now subject.
Well, here is an important operation AND-ing.

Using AND-ing operation the device can easily determine which network IP address belongs to and forward it in that direction and that enable Router that continuously communicate with each other, and both can happen in a split second, that I say in milliseconds or microseconds.

Furthermore, you must be aware that the IP addressing thoughtfully hierarchy as you can see in Figure10 and Figure10a.
This means that on top of the IP address (a network) and below that branch out from the other IP address (subnet).
I hope that the operation "AND-ing" clear.

We come to the steps below us, linked to the IP addresses that are divided (ie. When we perform subnetting.)
This is again part of the IP address range, by which we can change the network mask that subnet mask so we have VLSM (Variable Length Subnet Mask) and this is the one variable number that is written to the IP address.
Let's go to the next page of tutorial.