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1. 1. IP Addressing/Subnetting Simplified Brian Sterck May 6, 2005
2. 2. Class ASubnetting Options
3. 3. Class BSubnetting Options
4. 4. Class CSubnetting Options
5. 5. Brain Benders
6. 6. More Tools…
7. 7. Practical Example
8. 8. Do we have enough addresses?• How many addresses have been allocated?• How many are needed?
9. 9. Address Allocation• Total Address Needed: LANs = 14+10+19+23+6+17+14 = 103 WANs = 4+4+4+4+4+4 = 24 Total = 103 + 24 = 127
10. 10. Understanding IP Requirements• Subnetworks on the LAN/WAN need to be issued using perfect powers of 2• 22 = 4• 23 = 8• 24 = 16• 25 = 32• 26 = 64• 27 = 128
11. 11. Scaling Subnets• With a requirement of 23 nodes…• The next perfect power of 2 that meets this need = 32• 25 = 32 5 host bits needed• Last Octet is then represented as: – A.B.C.NNNHHHHH N=Network H=Host – 11111111.11111111.11111111.11100000
12. 12. Subnetting ExamplesSubnetMask SubnetMask # Hosts255.255.255.0 /24 256 (254)255.255.255.128 /25 128 (126)255.255.255.192 /26 64 (62)255.255.255.224 /27 32 (30)255.255.255.240 /28 16 (14)255.255.255.248 /29 8 (6)255.255.255.252 /30 4 (2)
13. 13. Practical Example
14. 14. Address Allocation• Total Addresses Needed: LANs = 16+16+32+32+8+32+16 = 152 = /28 + /28 + /27 + /27 + /29 + /27 + /28 = 152 WANs = 4+4+4+4+4+4 = 24 = /30 + /30 + /30 + /30 + /30 + /30 = 24 Total = 103 + 52 = 157
15. 15. Reference Points• Use numbers, symbols, letters to represent each LAN / WAN link• Use some consistent method for assignment – Size of Subnetwork – Location – Zone or Distribution Point
16. 16. Assign Reference Points
17. 17. Subnetting Options
18. 18. Subnetting Options (cont.)
19. 19. VLSM and Routing Protocols• Does your routing protocol support varying the length of the subnet mask from one interface to another?• Can you re-subnet a subnet differently from one interface to another and still advertise that subnetwork via RIPv1, RIPv2, OSPF, EIGRP, ISIS, BGP?
20. 20. Routing Protocols• Supporting VLSM – RIP version 2 – EIGRP – OSPF – ISIS• Not Supporting VLSM – IGRP – RIP version 1
21. 21. Which Routing Protocols willadvertise all Networks correctly?
22. 22. Non-VLSM capable RoutingProtocols will work just fine!
23. 23. Problem!• The 192.168.20.0 /24 network gives us: – 1 Network – 254 Nodes Available for Assignment• 13 Subnetworks Required• Network Demands range from 4 – 32 nodes per LAN / WAN segment
24. 24. Start Subnetting
25. 25. Subnetting
26. 26. Subnetting
27. 27. Box Diagram Alternate