Hi, this is your host Habib, and now that we know the functions of each layer of the two communication models, the OSI and the TCP IP. I will talk about ipv4 address in this lesson. ipv4 is still the dominant standard of Internet Protocol. An ipv4 address is a 32 bit logical address. As you know, the physical address is always the MAC address of the device. It is presented in decimal format with four octet separated by dots.
And in here, the example is 192 168 dot one dot one. There are about two to the raise of the power 32 or 4.3 billion IP addresses around the world. Not all of these IP addresses are route. And I'll explain that there are IP addresses that are that are not routable. And I will explain that in the next slide. We're moving on to the classes of ipv4.
There are five classes of ipv4 Class A, which starts from zero dot zero dot zero dot zero to 172 dot 255255255. Class B that starts from 128 dot zero dot zero dot zero to 191 dot 255255255. Class C and it starts from 192 dot zero dot zero dot zero to two to three dot 255255255 Class D and it starts from two to four dot zero dot zero dot zero to 239 dot 255255255. This block of addresses is only reserved for multi casting. Then you have the Class II addresses that starts from 240 dot zero dot zero dot 0225 525-525-5255. And this block of IP addresses is reserved for experimental purposes.
Along the way RFC 1918 addresses were introduced RFC 1918 mandate was to help to conserve the IP addresses that are routable over the internet because as you know, we only have 4.3 billion addresses. The Internet Assigned Numbers Authority which is also known as reserved in each class, a block of IP addresses that can be used privately. Now these private IP addresses are not right or not routable but can be used by anyone. Class A, the block that was chosen from class A starts from 10 dot zero dot zero dot zero to 10 dot 255255255. The class B block that was blocked for private usage is 172 dot 16 dot zero dot zero to 172 dot 30 One dot 255255. And the class C addresses that is blocked for private use is 192 dot 168 dot zero dot zero to 192 dot 168 dot 255255.
Someone may ask, well these IP addresses are not routable How would they communicate with the internet world? Well, you will need a mechanism to have these IP addresses convert to a public IP address in your network. And that is called netting. I will be talking about netting in the next lesson. Please follow along. Thank you very much