1. معمل رقم (3) IP Address

2. the 5 different Classes

3. In the above table, you can see the 5 Classes
In the above table, you can see the 5 Classes. Our first Class is A and our last is E. The first 3 classes ( A, B and C) are used to identify workstations, routers, switches and other devices whereas the last 2 Classes ( D and E) are reserved for special use.

4. As you would already know an IP Address consists of 32 Bits, which means it's 4 bytes long. The first octec (first 8 Bits or first byte) of an IP Address is enough for us to determine the Class to which it belongs. And, depending on the Class to which the IP Address belongs, we can determine which portion of the IP Address is the Network ID and which is the Node ID

5. For example, if I told you that the first octec of an IP Address is "168" then, using the above table, you would notice that it falls within the range, which makes it a Class B IP Address.

6. صممت عناويين Class A من اجل الشبكات الكبيرة ، و Class B للشبكات المتوسطة ، وClass C للشبكات الأصغر جحماً

7. Understanding the Classes
We are now going to have a closer look at the 5 Classes. If you remember earlier I mentioned that companies are assigned different IP ranges within these classes, depending on the size of their network. For instance, if a company required 1000 IP Addresses it would probably be assigned a range that falls within a Class B network rather than a Class A or C.

8. Introducing Network ID and Node ID concepts
يتكون عنوان IP Address من جزئيين:
(Network ID) وهو يحدد عنوان الشبكة التي ينتمي اليها الجهاز .
(Node ID , or Host ID) وهو يحدد عنوان الجهاز .

10. السؤال الأن كيف يمكن ان نحدد اي الجزيين يدل على عنوان الشبكة وايهما يدل على عنوان الجهاز ؟
للاجابة على هذا السؤال

12. Explanation
The table above might seem confusing at first but it's actually very simple. We will take Class A as an example and analyze it so you can understand exactly what is happening here
Any Class A network has a total of 7 bits for the Network ID (bit 8 is always set to 0) and 24 bits for the Host ID. Now all we need to do is calculate how much 7 bits is:

13. 2 to the power of 7 = 128 Networks and for the hosts : 2 to the power of 24 = 16,777,216 hosts in each Network, of which 2 cannot be used because one is the Network Address and the other is the Network Broadcast address (see the table towards the end of this page). This is why when we calculate the "valid" hosts in a network we always subtract "2". So if I asked you how many "valid" hosts can you have a on Class A Network, you should answer 16,777,214 and NOT 16,777,216.
Below you can see all this in one picture:

15. The same story applies for the other 2 Classes we use, that's Class B and Class C, the only difference is that the number of networks and hosts changes because the bits assigned to them are different for each class.

16. Class B networks have 14 bits for the Network ID (Bits 15, 16 are set and can't be changed) and 16 bits for the Host ID, that means you can have up to '2 to the power of 14' = 16,384 Networks and '2 to the power of 16' = 65,536 Hosts in each Network, of which 2 cannot be used because one is the Network Address and the other is the Network Broadcast address (see the table towards the end of this page). So if I asked you how many "valid" hosts can you have a on Class B Network, you should answer 65,534 and NOT 65,536.

18. Class C networks have 21 bits for the Network ID (Bits 22, 23, 24 are set and can't be changed) and 8 bits for the Host ID, that means you can have up to '2 to the power of 21' = 2,097,152 Networks and '2 to the power of 8' = 256 Hosts in each Network, of which 2 cannot be used because one is the Network Address and the other is the Network Broadcast address (see the table towards the end of this page). So if I asked you how many "valid" hosts can you have a on Class C Network, you should answer 254 and NOT 256.

20. Now, even though we have 3 Classes of IP Addresses that we can use, there are some IP Addresses that have been reserved for special use. This doesn't mean you can't assign them to a workstation but in the case that you did, it would create serious problems within your network. For this reason it's best that you avoid using these IP Addresses.

21. Avoidance IP
The following list shows the IP Addresses that you should avoid using:

22. IP Address Classes and Structure
Ping برنامج يستطيع أن يخبرك ان كان طقم البروتوكولات TCP/IP المستخدم للاتصال مع الجهاز الآخر يعمل بشكل طبيعي . وبمعنى آخر للتأكد من قدرة الحاسب على ارسال واستقبال البيانات .
الصيغة العامة لاستخدم Ping : Ping target_address
الأمر ipconfig لمعرفة عنوان الجهاز علي الشبكة .

23. The End