1. تقسيم الشبكات Subnetting

2. ما هو الـ IP Subnetting؟
هو تقسيم رقم شبكة Network Address إلى شبكات أصغر
فكرة التقسيم تتلخص في حجز بعض البتات من جزء عنوان الجهاز في عنوان IP لتخصيصها كعنوان للشبكة الفرعية مما يعني تقليل عدد العناوين المتاحة للاستخدام من قبل الأجهزة.

3. الفوائد التي سنجنيها من عملية التقسيم:
1- تقليل ازدحام الشبكة Reduce Network Traffic . أذا كان عندك شبكة كبيرة، بعض الأجهزة تقوم بإرسال بث Broadcast إلى جميع الأجهزة وهذا يؤدي إلى ازدحام الشبكة. ولكن إذا قمت بتقسيم هذه الشبكة إلى شبكات صغيرة ووضعت بينهم Router سيؤدي ذلك إلى تحسين أداء الشبكة حيث أن الـ Router سيسمح فقط بمرور المعلومات في حالة نقل البيانات بين جهاز في شبكة وأخر في شبكة أخرى. ولن يسمح الـ Router بمرور البث Broadcast إلى الأجهزة في الشبكة الأخرى.
2. تسهيل إدارة الشبكة وسهولة معرفة المشكلة إذا حدثت لقلة عدد الأجهزة بالشبكة الواحدة.

4. بشكل عام يجب على مدير الشبكة قبل التفكير في تقسيمها أن يحدد بعض الأمور كما يلي: 1- عدد الشبكات الفرعية التي يريد الحصول عليها. 2- عدد الأجهزة التي يريد من كل شبكة فرعية أن تحتويها.

5. مبادئ شبكات الحاسب ( الفصل الرابع )
IP Addressing
32 bits
Dotted Decimal
Network
Host
255
255
255
255
Maximum
Layer 3 of 3:
In layer 3, an example of dotted-decimal format and binary are displayed.
Emphasize: IP address format is dotted-decimal. Dotted-decimal makes it easy to work with IP addresses. However, in this course we will work with the addresses on the bit level, so we will convert these addresses into binary, make changes to them, and convert them back.
The central authority for addresses is the Internet Assigned Numbers Authority.
Note: This most common form of addressing reflects the widely used IP version 4. Faced with the problem of depleting available addresses, Internet Engineering Task Force (IETF) work is under way for a backward-compatible next generation of IP (IPng, also called IP 6).
IP 6 will offer expanded routing and addressing capabilities with 128-bit addresses rather than the 32-bit addressing shown on the graphic. Addresses from both IP versions will coexist. Initial occurrences will probably be at locations with address translator software and firewalls.
Binary
172 16
122
204
Example Decimal
Example Binary
مبادئ شبكات الحاسب ( الفصل الرابع )

6. IP Address Classes Class A: Class B: Class C: Class D: Multicast
8 bits
8 bits
8 bits
8 bits
Class A:
Class B:
Class C:
Class D: Multicast
Class E: Research
Network
Host
Network
Host
Purpose: This graphic describes the three most common classes of IP address.
Emphasize: Discuss classes of addresses. Each address contains information about the network number and the host number of the device. Class A addresses are for very large organizations. Class B addresses are for smaller organizations, and Class C addresses for even smaller ones.
As the number of networks grows, classes may eventually be replaced by another addressing mechanism, such as classless interdomain routing (CIDR). RFC 1467, Status of CIDR Deployment in the Internet, presents information about CIDR. RFC 1817, CIDR and Classful Routing, also presents CIDR information.
Network
Host

10. أقنعة الشبكة الفرعية Subnet Masks Default Mask

11. مبادئ شبكات الحاسب ( الفصل الرابع )
Default Mask
مبادئ شبكات الحاسب ( الفصل الرابع )

12. مبادئ شبكات الحاسب ( الفصل الرابع )
Default subnet
مبادئ شبكات الحاسب ( الفصل الرابع )

13. Subnet Mask Exercise Answers
Address
Subnet Mask
Class
Subnet B
Layer 2 of 2:
Purpose: This answers to the exercise are given in the figure.
Note: Students can also find the answers to this exercise in the “Answers” appendix. A A

14. Addressing without Subnets
Purpose: This figure explains what networks look like without subnets.
Without subnets, use of network addressing space is inefficient.
The Class B network is like a highway with no exits—there is no place to exit, so all of the traffic is in one line.
…...
Network

15. Subnet Mask with Subnets

16. Addressing with Subnets
Purpose: This figure describes network structure when subnets are used.
Emphasize: The host bits of an IP address can be subdivided into a subnetwork section and a host section. The subnetwork section in this example is the full third octet.
Point out the difference in the addressing between the previous slide and this slide.
A subnetted address space is like a highway with exits.
A network device uses a subnet mask to determine what part of the IP address is used for the network, the subnet, and the device ID.
A subnet mask is a 32-bit value containing a number of one bits for the network and subnet ID and a number of zero bits for the host ID.
Given its own IP address and subnet mask, a device can determine if an IP packet is destined for 1) a device on its own subnet, 2) a device on a different subnet on its own network, or 3) a device on a different network.
A device can determine what class of address the device has been assigned from its own IP address. The subnet mask then tells the device where the boundary is between the subnet ID and the host ID.
Network

17. ضع دائرة على Host من العناوين التالية :
ضع دائرة على network من على العناوين التالية :

18. ضع دائرة على Host من العناوين التالية :
ضع دائرة على network من على العناوين التالية :

22. Addressing Summary Example
172 16 2
160
Host 1
Mask
Layer 1 of 9:
Purpose: This example summarizes The IP addressing that was covered earlier in this chapter.
Emphasize:
In layer 1, convert the address to a binary host address.
Subnet 4
Broadcast
First
Last

23. Addressing Summary Example
172 16 2
160
Host 1
Mask 2
Layer 2 of 9:
Emphasize: In layer 2, write the subnet mask in binary.
Subnet
Broadcast
First
Last

24. Addressing Summary Example
172 16 2
160 3
Host 1
Mask 2
Layer 3 of 9:
Emphasize: In layer 3, draw a line after the recursive ones in the subnet mask.
Subnet
Broadcast
First
Last 7

25. Addressing Summary Example
172 16 2
160 3
Host 1
Mask 2
Layer 4 of 9:
Emphasize: In layer 4, fill in zeros beyond the vertical line for the subnet.
Subnet 4
Broadcast
First
Last

26. Addressing Summary Example
172 16 2
160 3
Host 1
Mask 2
Layer 5 of 9:
Emphasize: In layer 5, fill in ones beyond the vertical line for the broadcast address.
Subnet 4
Broadcast 5
First 6
Last

27. Addressing Summary Example
172 16 2
160 3
Host 1
Mask 2
Layer 6 of 9:
Emphasize: In layer 6, fill in 0s beyond the vertical line except for the last bit. Make that bit a 1. This is the first usable host address.
Subnet 4
Broadcast 5
First 6
Last

28. Addressing Summary Example
172 16 2
160 3
Host 1
Mask 2
Layer 7 of 9:
Emphasize: In layer 7, fill in 1s beyond the vertical line except for the last bit. Make that bit a 0. This is the last usable host address.
Subnet 4
Broadcast 5
First 6
Last 7

29. Addressing Summary Example
172 16 2
160 3
Host 1
Mask 2
Layer 8 of 9:
Emphasize: In layer 8, copy the binary network and subnetwork address from the top row into the lower rows. 8
Subnet 4
Broadcast 5
First 6
Last 7

30. Addressing Summary Example
172 16 2
160 3
Host 1
Mask 2
Layer 9 of 9:
Emphasize: In layer 9, convert binary back to dotted decimal. 9 8
Subnet 4
Broadcast 5
First 6
Last 7

31. &
Subnet mask
Source address
At the same
network connect
Subnet mask
At different
network
Connect to gateway 1
Destination address

32. Class B Subnet Example Subnet Address = 172.16.2.0
IP Host Address:
Subnet Mask:
Network
Network
Subnet
Host : :
Purpose: This figure shows an example of a Class B network with a subnet.
Subnet:
Broadcast:
Subnet Address =
Host Addresses = –
Broadcast Address =
Eight bits of subnetting

33. Class C Subnet Planning Example
IP Host Address:
Subnet Mask:
Network
Network
Network
Subnet
Host : :
Purpose: This figure shows an example of a Class C network with a subnet.
Emphasize: Contrast the Class C network subnet mask with the previous Class B example.
Subnet:
Broadcast:
Subnet Address =
Host Addresses = –
Broadcast Address =
Five Bits of Subnetting

39. تمارين

40. الحل
/30

41. Q 2 :
/27
كم الزيادة ؟
وعنوان أول شبكة ؟

42. الحل
/27
الزيادة ب 32
عدد الأجهزة ؟

43. الحل
/28
2^4-2=14

44.
2^5-2=30

45. Step 1: Convert to Binary
Step 1:
Translate Host IP Address and Subnet Mask into binary notation
Rick Graziani

46. Step 2: Find the Subnet Address
Determine the Network (or Subnet) where this Host address lives:
1. Draw a line under the mask
2. Perform a bit-wise AND operation on the IP Address and the Subnet Mask
Note: 1 AND 1 results in a 1, 0 AND anything results in a 0
3. Express the result in Dotted Decimal Notation
4. The result is the Subnet Address of this Subnet or “Wire” which is
Rick Graziani

47. Step 2: Find the Subnet Address
Determine the Network (or Subnet) where this Host address lives:
Quick method:
Find the last (right-most) 1 bit in the subnet mask.
Copy all of the bits in the IP address to the Network Address
Add 0’s for the rest of the bits in the Network Address
Rick Graziani

48. Step 3: Subnet Range / Host Range
Determine which bits in the address contain Network (subnet) information and which contain Host information:
Use the Network Mask: and divide (Great Divide) the from the rest of the address.
Use Subnet Mask: and divide (Small Divide) the subnet from the hosts between the last “1” and the first “0” in the subnet mask.
Rick Graziani

49. Step 4: First Host / Last Host
Host Portion
Subnet Address: all 0’s
First Host: all 0’s and a 1
Last Host: all 1’s and a 0
Broadcast: all 1’s
Rick Graziani

50. Step 5: Total Number of Subnets
Number of subnet bits 10
210 = 1,024
1,024 total subnets
Subtract one “if” all-zeros subnet cannot be used
Subtract one “if” all-ones subnet cannot be used
Rick Graziani

51. Step 6: Total Number of Hosts per Subnet
Number of host bits 6
26 = 64
64 host per subnets
Subtract one for the subnet address
Subtract one for the broadcast address
62 hosts per subnet
Rick Graziani

52. C - Range (192-223) A - Range (1-126) 255.0.0.0 B - Range (128-191)
C Range ( )