Original subtitles

So a network masks helps you know which portion of the address identifies a network and which portion

of the address identifies the node.

An IPv4 subnet mask consists of 32 bits, a sequence of one followed by a block of zero.

The trailing block of zeros designates that part as being the host identifier.

Class A, B and C networks have default masks, also known as natural masks, and these masks are.

Two five five zero zero zero for class class-A, 255.255.255.0 got zero for Class B and 255.255.255.0

for Class C networks.

So an IP address to a Class B network that has not been subnet.

We'd have an address mask pair similar to one three one one zero 7.1.2 being the address and 255.255.255.0

zero would be the subnet mask, right?

Now, in order to see how the mask helps you identify the network and node parts of the address, convert

the address and mask into binary numbers as seen on the slide.

So once you have the address in the mask represented in binary.

Then identification of the network and the host ID is a lot easier.

Any address bits which have corresponding mask bits set to one represent the network I'd.

And he addressed bits that have corresponding mask bits set to zero represent the host I.D..

So in this example, the first part, one three one eight one zero seven is the network part of the

IP address, where the rest 1.2 represents the host.

All devices on this segment share the same network ID and the same subnet mask.

Now you can customize the subnet mask to divide a network into many smaller portions.

So here's a little brain Tingler for you.

The Network ID may be expressed in classless inter domain routing or sidr notation written as the first

address of a network followed by a slash character and ending with a bit length of the prefix.

So in our example, one three one one zero seven eight zero zero one six is the prefix of the IPV four

network, starting at the given address, having 16 bits allocated for the network prefix and the remaining

16 bits reserved for host addressing.