Guide to TCP/IP, 4th Edition Jeffrey L. Carrell | Laura Chappell | Ed Tittel | James Pyles

Guide to TCP/IP, 4th Edition Jeffrey L. Carrell | Laura Chappell | Ed Tittel | James Pyles

Chapter 2 Solutions

Answers to Review Questions

1. c

2. c

3. b

4. c

5. a

6. a, c, d

7. c

8. True

9. True

10. b, d

11. a, b

12. a, b, d

13. c

14. b

15. c

16. a

17. b

18. b

19. b

20. a

21. d

22. a, d

23. a, b

24. c, d

25. d

Hands-On Projects Discussion

Hands-On Projects 2-1 through 2-3

The Bitcricket IP Calculator makes it much simpler to handle subnetting problems and provides IPv6 support. The tool allows you to input an IP address, number of subnets, number of hosts, number of bits in network or host portion of the address, and so forth, and automatically works out the results. If you plan to spend much time setting up or configuring IP networks, this tool is a must-have!

For Hands-On Project 2-3, the requirement that there be 32 subnets means that there must be five bits in the subnet mask. Calculating IPv6 addresses, including link-local and global addresses for a host is simple since the values for the host are automatically supplied.

Hands-On Project 2-4

Ralph Becker offers a straightforward and easy-to-use tutorial on IP address subnetting. Have the students step through each topic, and then browse the Internet resources links on the References and Sources on the Internet page. The material is older but should be considered “classic”.

Hands-On Project 2-5

There have been a number of recent RFCs regarding IPv6 addressing. RFC 4291 provides the more basic information about IPv6 address architecture, while RFC 6052 provides a more advanced view of the algorithmic translation of IPv6 addresses mapping to IPv4 addresses. The student isn’t meant to fully comprehend the content; this exercise introduces students to some of the standards that are the foundation of this version of IP.

Hands-On Project 2-6

Chapter 2 is largely a conceptual chapter, so there isn’t a great deal of material that can be immediately turned into “hands on” exercises. However, the chapter provides an excellent opportunity for students to gain some practice using basic networking utilities such as Ping and Ipconfig. Even students familiar with these common tools may not have practiced applying them to IPv6 addressing. This task will give them a brief introduction.

Hands-On Project 2-7

Accessing and manipulating a computer’s ARP table is another example of using an elementary networking tool to gather information. Again, this exercise is just a brief introduction to familiarize students who may not have accessed the ARP utility before.

Case Projects Discussion

Case Project 2-1

The key to easily solving this problem comes from assuming that each building will have its own single subnet. That means that the number of bits in the subnet mask needs to cover at least six addressable subnets. Thus, you can get by with three bits in the subnet mask in the second octet, because 2³ – 2 = 6. Because the default subnet mask for any Class A address is 255.0.0.0, this indicates a subnet mask of 255.224.0.0. Thus, the number of addressable hosts per subnet is 221 – 2 or 2,097,152 (because using 11 bits total for the network and subnet addresses leaves 21 bits left over for hosts). Thus, there is no impact whatsoever for upping the number of machines to 1,024 on any single network.

As a practical matter, it may be a good idea to use a four- or five-bit subnet mask for this situation on the off chance that the company may decide to extend the campus. Four bits provides a total of 14 subnets, and five bits a total of 30 subnets. Neither reduces the number of addressable machines to a level that’s worth worrying over (a four-bit subnet mask still produces 220 – 2, or 1,048,574 machines per building, whereas a five-bit subnet mask produces 219 – 2, or 524,286 machines per building—that’s a LOT of machines!).

Case Project 2-2

Where expense is a concern, reducing the size of the IP address block that must be leased monthly can matter a lot. For ABC Incorporated, this probably means using private IP addresses for all machines except the routers and servers. (With a total of five machines, this dictates a three-bit block that includes six usable addresses at minimum.)

Case Project 2-3

Many corporate IT administrators still manage their IP addresses using an Excel spreadsheet, so this might be a good time to convince your customer to invest in an IP Address Management (IPAM) application. Obviously, given their primary goal, IPv6 support is a must. You can research the available tools on the market and select one or two that you believe will best meet their needs.

Scalability means something very different when planning IPv6 address space than with IPv4. Most IT managers are locked into thinking of IP address design as working with a vanishing resource, creating subnets using Variable Length Subnet Masking (VLSM) to manufacture a subnet space barely able to host the required number of hosts, but no more. With IPv6, there is more than enough addresses to go around and you are free to create networks with a much larger number of addresses than you believe you'll ever need. Designs that would be considered extremely wasteful in IPv4 are perfectly acceptable using the IPv6 address space.

Everyone knows IPv4 is going away. It's only a matter of time until it becomes obsolete. It may be tempting to create an IPv6 design that offers some backward compatibility to IPv4, but that doesn't take into consideration IPv4 obsolescence and the administrative cost of managing two networks that barely talk to each other and then, reconfiguring your design once IPv4 support is removed. It makes more sense to design the network for IPv6 exclusively and then move forward to that goal.

IPv6 comes with built-in security support but you must still develop your address design to operate as efficiently as possible for the purposes of filtering IPv6 address bits. Suggest that addresses be designed so that any "bits" more likely to require filtering occur toward the beginning of the address. This will avoid having the filter scan deeper into the address field to find what it’s looking for and will prevent the filter rules list from getting too long.