Session 02 Subnetting

1. Session 02 Subnetting basic tasks are instrumental to the application of subnetting for networks

2. Objectives • Recognize the need for the restructuring of IP networks into subnetworks. • Recognize the design requirements for networks requiring custom subnet masks • Create the horizontal and vertical process tables • Interrelate the horizontal and vertical process tables • For a given requirement of subnets, determine the subnet mask • For a given requirement of hosts per subnet, determine the subnet mask • Apply the custom subnet masks to IP Addresses to provide valid Subnetwork IDs • Provide valid host ranges for a given subnetwork

3. IP Addressing (1/11) • IP address is logical numeric identifier • Assigned to an Network Interface Card (NIC) • DO NOT CONFUSE WITH MAC ADDRESS

4. IP Addressing (2/11) • Terminology • Bit - 0 or 1 • Byte – 8 bits • Octet – 8 bits • Network address – Destination used in routing • 10.0.0.0 • 172.16.0.0 • 192.168.22.0 • Broadcast – Send message to all nodes • 255.255.255.255 • Local broadcast – Send to nodes on network • 10.0.0.0 10.255.255.255 • 172.16.0.0 172.16.255.255 • 192.168.22.0 192.168.22.255

5. IP Addressing (3/11) • IP address • 32-bits long • Four bytes or octets • Expressed as dotted decimal • 198.137.240.92

6. Review: IP Addressing (4/11) • Class A Address • Between 1 – 126 • 127 is reserved for loopback tests • Private address 10.0.0.0

7. Review: IP Addressing (5/11) • Class B Address • Between 128 and 191 • Private address 172.16.0.0 through 172.31.0.0

8. Review: IP Addressing (6/11) • Class C Address • Between 192 and 223 • Private address 192.168.1.0 through 192.168.255.0

9. Review: IP Addressing (7/11) • Class D • Multicast • Between 224 and 239 • Class E • Experimental • Between 240 and 255

10. Review: IP Addressing (8/11) • Summary

11. Review: IP Addressing (9/11) • Network Ranges

12. Review: IP Addressing (10/11) • Host ID Ranges

13. Address Network all 0s Network all 1s Node all 0s Node all 1s All 0s All 1s Function This segment All segments This node Local broadcast Default route Broadcast Review: IP Addressing (11/11)

14. Review: Subnetting (1/2) • Reasons for subnetting • Reduced network traffic – Create broadcast domains • Optimized network performance • Simplified management • Enable spanning of large distances

15. Review: Subnetting (2/2) • Determine the number of required network IDs • One for each subnet • One for each WAN connection • Determine the number required host IDs per segment • One for each TCP/IP interface • One for each router interface • Create the following • One subnet mask for entire network • Unique subnet ID for each physical segment • Range of host IDs for each subnet

16. Default Subnet Masks(1/3)

17. Default Subnet Masks(2/3)

18. Default Subnet Masks(3/3)

19. Host Bits (1/2)

20. Host Bits (2/2) • Borrow host bits to create subnets

21. Subnetting and Routing

22. Custom Subnet Masks • Bits that correspond to network are set to 1 • Bits that correspond to host are set to 0 172. 16. 1.0 Network 255.255.255.0 Subnet mask

23. Creating the Delta Table (1/9) • Step 1: Table 9-columns x 3-rows • Step 2: Label rows Bits, Deltas, Subnets

24. Creating the Delta Table (2/9) • Step 3: Number bits 1, 2, 3, ….

25. Creating the Delta Table (3/9) • Step 4: Calculate the Delta values • Place 128 in the Bit 1 column

26. Creating the Delta Table (4/9) • Step 4: Calculate the Delta values • Place one-half of 128 (64) under the 2-bit

27. Creating the Delta Table (5/9) • Step 4: Calculate the Delta values • Place one-half of each preceding value under the respective column

28. Creating the Delta Table (6/9) • Step 5: Calculate subnet values • Place 128 under the delta value in the bit 1 column

29. Creating the Delta Table (7/9) • Step 5: Calculate subnet values • For the 2-bit column • Add the preceding value (128) and the delta value (64) • 128 + 64 = 192

30. Creating the Delta Table (8/9) • Step 5: Calculate subnet values • Repeat the process for the remaining values • Adding the preceding value and the delta value to provide each new entry

31. Creating the Delta Table (9/9) • Row 1: • Locate the number of bits • Row 2: • Create the values in row 3 • Used to calculate the resultant subnet IDs • Row 3: • Select the appropriate subnet mask

32. Create the Powers of 2 Table (1/3) • Multiplying the previous entry by two creates each succeeding entry

33. Create the Powers of 2 Table (3/3) • Used to determine bits required Corrected to remove all 0’s and all 1’s entries

34. Overview: Subnet Process (1/3) • Determine the number of bits required for the subnet mask Down and Over

35. Overview: Subnet Process (2/3) • Step 2: Locate the subnet mask Bits to Bits and Down

36. Overview: Subnet Process (3/3) Try it!

37. Class B Address (1/3) • 10 Subnets are required

38. Class B Address (2/3)

39. Class B Address (3/3)

40. Class C Address (1/2) • Six subnets are needed

41. Class C Address (2/2)

42. Trade-Off between Subnets & Hosts (1/2) • Number of bits used for subnetting • Number of subnets • Number of hosts/subnet • Future • Number of subnets • Number of hosts • Using more bits for the subnet mask than required • Saves you the time of reassigning IP addresses in the future.

43. Trade-Off between Subnets & Hosts (2/2)

44. Expanded Power of 2’s Table

45. 1000 Subnets (1/2) 1000 subnets requires 10 Bits

46. 1000 Subnets (2/2) 10 bits - 8 bits = 2 bits 255. 192

47. W A R N I N G You will need to be concerned with the following simple facts: • ·You will never have a host mask! • ·There is no such thing at a host mask! • ·A host mask does not exist!

48. Allocating Hosts (1/3 • Here’s the rule: • Determine the number of bits that are required for hosts • Subtract from the number of bits available • Result is the number of bits required for the custom subnet mask

49. Allocating Hosts (2/3) • 25 hosts per subnet • Requires 5 bits

50. Allocating Hosts (3/3) 8 - 5 = 3 3 bits -> 224