Academy Conference 2010 Frisco, Texas Teaching VLSM

1. Academy Conference 2010Frisco, Texas Teaching VLSM Barry Charter ~ North Arkansas College ~ Newly Retired  Shawn Dennis ~ Arkansas State University Mt. Home Arkansas CCNA CCAI July 19, 2010

2. Introduction Contact Information • Barry Charter bc_charter@yahoo.com • and • Shawn Dennis sdennis@asumh.edu

3. Importance of understanding VLSM • IPv4 address availability • CCNA exam • Further networking classes • Networking careers • What about IPv6?

4. Note: • INTRODUCE IP ADDRESSING AND BINARY THE FIRST DAY!! • Do not wait until the chapter on IP Addressing & Subnetting (D1 = Ch 5, E1 = Ch 6) to begin discussing the basics of IP addressing and what a subnet mask is. • Review IP Addressing and Binary daily • Practice makes perfect!!

5. Binary & IP Addressing • Understanding binary is extremely important • VLSM • Wildcard masks • IP Addresses • 32 bits • Dotted decimal format – 4 octets • Conversion for each octect • Practice converting IP Addresses from binary to decimal and vice versa. • Introduce binary system to students early in first course. I start the second day of class.

6. Dividing Address Space • The “Great Divide” • Where the division occurs between host bits and network bits • The “Magic Number” • Decimal value of the bit to the immediate left of “Great Divide” • Subnets will be in increments of the “Magic Number” • Example • Subnet Mask: /27 or 255.255.255.224 The “Great Divide” The “Magic Number” 128 64 32 16 8 4 2 1

7. Subnetting vs. VLSM vs. CIDR • Subnetting • Dividing network address space into equal size subnets • VLSM – Variable Length Subnet Mask • Divide network address space into unequal size subnets • Maximize use of IP address space • CIDR – Classless Inter-domain Routing • Subnet Mask specified using the prefix size • 255.255.255.0 = /24 • Use of VLSM requires use of routing protocols that support CIDR • RIPv2 • EIGRP • OSPF

8. Teaching MethodsMagic Box

9. Magic Box Method

10. What Length Subnet Mask Should You Use? – Practice, Practice, Practice...

11. What Length Subnet Mask Should You Use? – Practice, Practice, Practice...

12. Determine Network Portion of Subnets • Start with largest LAN • Working down in LAN size to point-to-point links • Determine number of bits needed to address the hosts • Larger LANs will have smaller CIDR prefixes • /30 prefix for point-to-point links • Formula: 2n – 2 • n – number of bits • 2 unusable addresses • Network address – first address in subnet • Broadcast address – last address in subnet

13. Teaching MethodSubnetting in a Box

14. Subnetting in a Box Method • Divide a piece of paper into smaller subnets • Value in top left corner of each section – network address • Value in bottom right corner of each section – broadcast address • Last network address is the value of the appropriate octet for subnet mask • As bits are borrowed the network is divided into smaller subnets. • New subnet mask is indicated by first address of last

15. Value in top left corner of each section – network addressValue in bottom right corner of each section – broadcast address

16. Value in top left corner of each section – network addressValue in bottom right corner of each section – broadcast address

17. Value in top left corner of each section – network addressValue in bottom right corner of each section – broadcast address

18. Value in top left corner of each section – network addressValue in bottom right corner of each section – broadcast address

19. Here is an example VLSM Exercise 1

20. Start with largest LANWorking down in LAN size to point-to-point links Example: list LANS in descending order 60 hosts 28 hosts 12 hosts 12 hosts There are 3 WAN links

21. Start with largest LANWorking down in LAN size to point-to-point links Example: Determine number of host bits needed 60 hosts – 6 host bits /26 28 hosts – 5 host bits /27 12 hosts – 4 host bits /28 12 hosts – 4 host bits /28 There are 3 WAN links – 2 host bits /30

22. Start with the largest LANWorking down in LAN size to point-to-point links 60 hosts – 6 host bits /26 28 hosts – 5 host bits /27 12 hosts – 4 host bits /28 12 hosts – 4 host bits /28 There are 3 WAN links – 2 host bits /30

23. Start with the largest LANWorking down in LAN size to point-to-point links 60 hosts – 6 host bits /26 28 hosts – 5 host bits /27 12 hosts – 4 host bits /28 12 hosts – 4 host bits /28 There are 3 WAN links – 2 host bits /30

24. Start with the largest LANWorking down in LAN size to point-to-point links 60 hosts – 6 host bits /26 28 hosts – 5 host bits /27 12 hosts – 4 host bits /28 12 hosts – 4 host bits /28 There are 3 WAN links – 2 host bits /30

25. Start with the largest LANWorking down in LAN size to point-to-point links 60 hosts – 6 host bits /26 28 hosts – 5 host bits /27 12 hosts – 4 host bits /28 12 hosts – 4 host bits /28 There are 3 WAN links – 2 host bits /30

26. PracticePacket Tracer Activities Exercise 2 20 min

27. Start with the largest LANWorking down in LAN size to point-to-point links Ex 2

28. PracticePacket Tracer Activities Exercise 3 20 min

29. Start with the largest LANWorking down in LAN size to point-to-point links Ex 3

30. PracticePacket Tracer Activities Exercise 4 20 min

31. Start with the largest LANWorking down in LAN size to point-to-point links

32. Teaching Resources

33. Cisco Learning Institute

34. Other Resources • Presentations • http://www.cisco.com/web/learning/le31/le46/cln/clp/fastlane/Subnet_Calculator/index2.htm • www.learntosubnet.com • Subnet Calculators • http://www.cisco.com/cgi-bin/Support/IpSubnet/home.pl • www.solarwinds.com • www.subnet-calculator.com/cidr.php • http://www.subnetonline.com/pages/subnet-calculators/ip-subnet-calculator.php • http://www.wildpackets.com/resources/free_utilities/ipsubnetcalc

35. Questions? Thank you for attending! DON’T FORGET TO TURN IN EVALUATION 