Chapter 10


1:

Imagine that a router receives a packet over an Ethernet. What does the router look at inside the IP packet to decide what to do with the packet?

A1:

Answer: The destination IP address

2:

PC1 sits on an Ethernet, with a web server on another Ethernet. A router, R1, is connected to both Ethernets. How does PC1 get its HTTP request to the web server?

A2:

Answer: PC1 sends the packet to the router, which then forwards the packet to the web server.

3:

PC1 sits on an Ethernet network, along with R1, and R1 and R2 are connected to a second Ethernet. Finally, R2 is connected to a third Ethernet, along with a web server. PC1's IP address is 5.5.5.5, and the server's is 6.6.6.6. What IP address is in the destination IP address field of a packet sent from PC1 to the web server?

A3:

Answer: 6.6.6.6

4:

PC1 sits on an Ethernet network, along with router R1. Routers R1 and R2 are connected to a second Ethernet. Finally, R2 is connected to a third Ethernet, along with a web server. PC1's IP address is 5.5.5.5, and the server's is 6.6.6.6. When the web server sends a packet back to PC1, what IP address is in the source IP address field of the packet?

A4:

Answer: 6.6.6.6

5:

For Class B networks, what is the range of numbers allowed for the first octet?

A5:

Answer: 128 through 191, inclusive

6:

For Class C networks, what is the range of numbers allowed for the first octet?

A6:

Answer: 192 through 223, inclusive

7:

How many IP addresses exist in Class A network 7.0.0.0?

A7:

Answer: 2242, or 16,777,214. (If you answered with something like "more than 16 million," that's close enough!)

8:

How many IP addresses exist in Class B network 166.5.0.0?

A8:

Answer: 2162, or 65,534. (If you answered with something like "more than 65 thousand," that's close enough!)

9:

How many IP addresses exist in Class C network 192.55.0.0?

A9:

Answer: 254

10:

Describe the structure of a Class A IP address.

A10:

Answer: Class A addresses have two parts: a network part and a host part. The network part is 1 octet long, and the host part is 3 octets long.

11:

Describe the structure of a Class C IP address.

A11:

Answer: Class C addresses have two parts: a network part and a host part. The network part is 3 octets long, and the host part is 1 octet long.

12:

What is an octet?

A12:

Answer: An octet is a string of 8 bits, typically referring to a portion of an IP address. IP addresses contain 4 octets, making them 32-bit numbers.

13:

Define the term IP network. List a sample network, along with the first and last valid IP addresses.

A13:

Answer: An IP network is a set of IP addresses that have the same numeric value in the network part of the addresses. Class A network 1.0.0.0, for example, requires that all addresses begin with 1. 1.0.0.1 is the first valid IP address, and 1.255.255.254 is the last.

14:

All hosts on a particular LAN segment use IP addresses that begin with 150.1.1. What network number describes the network in which these addresses reside?

A14:

Answer: Because 150 is in the range for Class B addresses, the network number is 150.1.0.0. It is formed by using the first two octets of the actual addresses, followed by 0s.

15:

All hosts on a particular LAN segment use IP addresses that begin with 150.1.1. Subnetting was used, treating the first 3 octets as the subnet. What subnet number is used to represent the subnet?

A15:

Answer: 150.1.1.0. With subnetting, the subnet number includes the same value as the individual IP addresses, for the network and subnet parts of the addresses, and all 0s in the host part.

16:

What is the main motivation for using IP subnetting?

A16:

Answer: Without subnetting, each physical network requires a separate Class A, B, or C network. Class A and B networks have far too many IP addresses compared to the actual need for addresses. Subnetting reduces the waste of the IP address space.

17:

Describe how subnetting is accomplished, particularly how it changes or relaxes some rules about how IP addresses are structured.

A17:

Answer: Without subnetting, Class A, B, and C rules define what must be true about addresses for them to be considered part of the same group. With subnetting, a longer portion of the addresses must be in common for the addresses to be considered part of the same group. Using the longer portion of the addresses to identify the group allows you to define more groups, while making each group smaller.

18:

Imagine that Class B network 128.1.0.0 is subnetted by treating the first 3 octets as if they were the network number. A network diagram requires four subnets. Describe how you might go about deciding what the addresses should look like in each subnet.

A18:

Answer: In this case, the first 3 octets of addresses in each subnet must be the same number. So, in one subnet, all addresses could start with 128.1.1; in another, 128.1.2; in another, 128.1.3; and in the fourth subnet, 128.1.4.

19:

What two main functions does the IP protocol define?

A19:

Answer: Logical IP addressing and end-to-end routing of packets




Computer Networking first-step
Computer Networking First-Step
ISBN: 1587201011
EAN: 2147483647
Year: 2004
Pages: 173
Authors: Wendell Odom

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