It is a good idea to protect your Web server by using NAT on the Web server itself.

36. (p. 187) Every IP node on a network has a routing table. 
TRUE

37. (p. 194) It is a good idea to protect your Web server by using NAT on the Web server itself.
FALSE

38. (p. 214) Secure Shell (SSH) is a terminal emulation program that is useable over a LAN connection.
TRUE

39. (p. 204) Less efficient than RIP, OSPF sends routing information at regular intervals, even if nothing has changed.
FALSE

40. (p. 185) Each column in a routing table defines a single route.
FALSE

41. (p. 183) Routers work primarily with the source IP address of each packet.
FALSE

42. (p. 210) The first thing you should do with a new router is to plug it into an existing network.
FALSE

43. (p. 189) In a routing table, whenever the gateway address and the interface address are the same, it's a local connection.
TRUE

44. (p. 192) NAT is not routing.
TRUE

45. (p. 204) BGP is used between routers inside a single Autonomous System.
FALSE

46. (p. 191) The IANA assigned the last of the IPv4 addresses as of February 2011.
TRUE

47. (p. 192) NAT extended the useful life of IPv4 addresses on the Internet for many years.
TRUE

48. (p. 193) With NAT, the router replaces the destination IP address of a computer with its outside interface address on outgoing packets.
FALSE

49. (p. 198) When making routing decisions, higher-value metrics are used first.
FALSE

50. (p. 198) The hop count metric counts the number of routers between two networks.
TRUE

Fill in the Blank Questions
 

51. (p. 183) A router must have at least _______________ interfaces (connections).
two

52. (p. 184) A router drops packets into its queue based on the _______________.
time the packet arrived at the router

53. (p. 215) The vast majority of routers in homes or small offices link the LAN to the Internet using the WAN connection to connect to a(n) _______________.
ISP

54. (p. 185) Each _______________ in a routing table identifies a specific criterion.
column

55. (p. 184) All routers have an internal _______________ that aids them in determining where to send packets.
routing table

56. (p. 186) When a packet's destination network ID is the same as the directly connected network, you don't need a gateway. Therefore, a router may show a value of _______________ or the IP address of the directly connected port appears in the Gateway column.
all zeroes/0.0.0.0

57. (p. 189) When reading a routing table, whenever the gateway and the interface are the same, it's a(n) _______________ connection.
local

58. (p. 196) While routers have _______________ routes, most routers also can update their routes dynamically.
static

59. (p. 199) The basis of distance vector routing protocols is some form of _______________.
total cost

60. (p. 203) Autonomous Systems communicate with each other using a(n) _______________ protocol.
exterior gateway

61. (p. 202) RIP is a(n) _______________ routing protocol.
distance vector

62. (p. 204) The Border Gateway Protocol (BGP) uses a(n) _______________ algorithm, but BGP routers only pass changes in their routing tables—not the entire table, drastically reducing traffic that occurs when the entire table is passed.
distance vector

63. (p. 202) _______________ is a routing protocol that supports CIDR, sends routing table updates at random intervals, and has security built-in, but only works with a maximum hop count of 15.
RIPv2

64. (p. 204) The current version of the Border Gateway Protocol is _______________.
BGP-4

65. (p. 192) To physically connect your local TCP/IP network to the Internet or to any other TCP/IP network, you must have a(n) _______________.
gateway router

66. (p. 192) While not a routing function, _______________ capability is often an additional feature of a router, and it was created both to reduce the demand for public IP addresses and to provide more security to systems.
Network Address Translation (NAT)

67. (p. 194) Many NAT routers have a feature called _______________ that directs incoming traffic based on port number to a specific computer in the network.
port forwarding

68. (p. 186) When you see a zero (0) in a routing table, it means _______________.
anything or any value

69. (p. 189) Each _______________ in a routing table defines a single route.
row

70. (p. 185) Your router uses a combination of the destination LAN IP and _______________ to determine if the packet matches a route.
subnet mask

71. (p. 184) With TCP/IP a router can have more than one route to a destination, and therefore consults its routing table before selecting the _______________ route for a packet to take to its destination.
best, most efficient, shortest

72. (p. 188) Although the Internet is often described as a network of computers, the text indicates that it is really a network of _______________.
routers

73. (p. 216) What appears to be a router problem is more likely a non-router connection problem because ___________________.
routers are very reliable/routers do not fail very often

74. (p. 189) Any 127/8 address is a(n) ___________________ address.
loopback

75. (p. 217) ___________________ is a command-line utility that records the route between any two hosts on a network.
traceroute

76. (p. 204) All the Autonomous Systems of the Internet communicate with each other using the ___________________.
Border Gateway Protocol (BGP-4)

77. (p. 194) The ___________________ is a fixed, predetermined number that defines the function or session type.
destination port

78. (p. 194) Network address translation (NAT) uses a(n) ___________________ to track the source information from a packet that it will use to match up any incoming packets destined for a local machine.
NAT translation table

79. (p. 194) When a receiving system responds to a received packet, it reverses the ___________________.
IP addresses and ports

80. (p. 201) Unlike RIP routers, OSPF routers keep ___________________ to the same network ID in their routing tables.
multiple routes

81. (p. 202) Two key differences between RIPv1 and RIPv2 are that RIPv1 does not support __________ and __________.
authentication, VLSM

82. (p. 183) A(n) _________ joins two or more networks (subnets or LANS) or WANS together.
router

83. (p. 193) Basic NAT is also known as overloading NAT or __________.
PAT

84. (p. 193) __________ changes private source address and port number to something usable on the Internet.
PAT

85. (p. 196) Home routers often have __________ turned on by default.
NAT

Essay Questions
 

86. (p. 183) Write a descriptive sentence describing the basic function of a router. 

A router is a network device or software, working at Layer 3 of the OSI model, which forwards packets based on their destination IP address.

87. (p. 188) What two command-line commands can you use to display the contents of a routing table on a Windows PC? 

Two command-line commands that you can use from within Windows to view the contents of the PC's routing table are netstat-r and route print.

88. (p. 187) What are the five columns of information provided for each route in a routing table (actual names can vary by router or operating system)? Point out the one column not seen on a home router. 

The five columns of information in most routing tables include the Network Destination, the Netmask (or Subnet Mask), the Gateway, the Interface, and the Metric. The last item is not in a routing table for a home router.

89. (p. 187) Since most client computers send packets out a single interface, why is it necessary for an IP client to have its own routing table? 

There are computers that have more than one NIC, but routing tables are necessary on computers even for that majority of computers with only one NIC. A routing table is necessary for many instances. For instance, how does your computer know what to do with a packet with a destination address of 127.0.0.1? The TCP/IP software in the operating system must also decide if it should send a packet directly to a computer on the LAN, or to the gateway. These decisions are made just as they are on a router—by determining the destination network ID of the packet, and then looking up the correct route in the routing table.

90. (p. 186) Explain how a router determines the correct route to use. 

A router, or the IP software in a PC, first determines the network ID of a packet's destination IP address. Then it goes through each route (line) in the routing table to find all the routes that will get the packet to its destination network. If more than one route will work, it will use the route with the lowest cost.

91. (p. 210) How can an administrator connect to a new router to begin the configuration process? 

The most common method an administrator uses to connect to a new router, especially a Cisco router, to begin the configuration process is to use a special serial connection, connecting to it with a rollover or Cisco-designed Yost cable. One end connects to a special configuration port on the router, and the other connects to a PC. Then the administrator uses a terminal program to connect to the new router.

92. (p. 209) Describe the methods for adding routes to a routing table. 

Routes are added to a routing table manually, detected by a router at setup, or dynamically. An administrator adds static routes to a router manually, or when the router is first brought on line. Changes are added dynamically with the use of specialized routing protocols installed and turned on in the router. Most routers build their routing tables using a combination of static and dynamic methods. Dynamic routing protocols are used by routers to keep up with changes in routing connections, as links are added or go down.

93. (p. 209) In general terms, explain what happens when a router connection goes down on the Internet. 

The Internet is a mesh of routers with multiple routes to each other for the sake of redundancy. Therefore, when a router goes down, the routers will automatically switch to alternate routes.

94. (p. 174) Describe the two situations in which a routing table would not have default routes. 

One situation in which a router would not have a default route in its routing table is in a private network, not on the Internet, in which every router knows every other router. Another is in the Tier One backbone where routers make the main connections of the Internet.

95. (p. 186) What are the two disadvantages or RIPv1 compared to RIPv2? 

RIPv1 does not have VLSM support, whereas RIPv2 does. RIPv1 updates at a fixed interval, while RIPv2 updates at random intervals. RIPv1 has no authentication, but this is built into RIPv2.

96. (p. 208-209) Explain EIGRP. 

EIGRP is Enhanced Interior Gateway Routing Protocol; it is the latest version of a proprietary protocol developed by Cisco and only found on Cisco routers. The first generation of this protocol was Interior Gateway Routing Protocol (IGRP).

97. (p. 193) Describe how PAT works, explaining how this protects the computers on a private LAN. 

In most uses of PAT, a single public IP address is shared by a number of computers that share a private network ID. Overloaded NAT replaces the outgoing packet's source IP address with the NAT router's external interface address, and adds the destination IP address and the source ephemeral port to the NAT translation table. When the receiving system returns a packet, the overloaded NAT router reverses the IP addresses and ports and checks the NAT translation table to determine which local IP address to use for sending the packet to the correct computer.

98. (p. 191 and 195) What two things does NAT hide in order to protect your system from security threats? 

NAT hides internal IP addresses and ports to protect systems on the local LAN from security threats from outside networks, such as the Internet.

99. (p. 192) To systems on the Internet, what does your entire private network look like if you are using NAT? 

When you are using NAT, to the systems on the Internet your entire private network appears to be one system.

100. (p. 198-199) In a routing table entry, what does metric mean? 

The metric represents the cost of the route. This can be in simple hops, based on the speed of the link as well as the number of hops, or it can be a value an administrator enters to achieve a correct cost relative to other routes.

101. (p. 204) Describe Border Gateway Protocol (BGP), including the purpose of BGP. 

The purpose of the Border Gateway Protocol, the latest version of which is BGP-4, is for communication between Autonomous Systems' edge routers.

102. (p. 186) Describe how and when a router uses the default route. 

The default route is the one the router will use unless another line in the routing table gives a route for the packet.

103. (p. 204) Define an edge router, including both its role and the larger system within which it exists. 

An edge router is a router that provides the communications between its Autonomous System and the edge router for another Autonomous System.

104. (p. 204) Explain why an Autonomous System (AS) using BGP-4 on its edge routers will use OSPF internally. 

An AS using BGP-4 on its edge routers will use OSPF internally because OSPF was designed to work within a single AS. This protocol converges much faster than, and is more efficient than, RIP.

105. (p. 204) Define a link state dynamic routing protocol. 

A link state dynamic routing protocol announces and forwards individual route changes as they appear, rather than sending the entire routing table at a fixed interval, as do distance-vector dynamic routing protocols.

106. (p. 183) Briefly describe the basic function of a router, regardless of its size. 

The basic function of a router is to examine packets and send them to the proper destination.

107. (p. 217) Describe a command that marks the entire route a ping packet travels between your computer and the intended destination. 

The traceroute command sends a ping packet to another host. At each router along the way, it returns information about the router. The Windows version of this command is tracert.

108. (p. 217) Describe the my traceroute (mtr) command, distinguishing it from another command used to trace the travels of a packet through routers. 

mtr is like the traceroute command in that it marks the entire route a ping packet travels between your computer and the intended destination. It differs from the older command in that it is dynamic, continually updating the route you've selected.

109. (p. 215-216) Briefly describe the four steps to basic router configuration. 

Before you set up a router you need to gather information from your ISP concerning the WAN side of the router, then you must connect to the router per the manufacturer's instructors. Then you can begin Step 1: setting up the WAN side. If you paid for a static IP, you will enter this into the WAN setting in the router configuration utility. If you are setting up a home router, the WAN side most likely uses DHCP to receive its IP address, so you would select DHCP or "automatic" in the WAN settings. In Step 2, you set up the LAN side of the router. You chose a network ID (usually selecting this from the private IP address pool). Then you will assign the LAN side an address from the network ID. Step 3 involves establishing routes, which many routers will do automatically. If you must add more routes, you can add them using the router configuration utility. On a Cisco router, this may require using the correct IOS command. Finally, Step 4, Configure a Dynamic Protocol, only applies if this is not a home router and is on a network with several routers. You must do this for each NIC and may only require turning on the dynamic protocol.

110. (p. 194) When a NAT router sends a packet containing a source port to an outside destination, how does the destination system treat the source port number in the return packet? 

When a system on the Internet receives a packet with an source port, it uses the source port as a destination port in the return packet.

111. (p. 212) You are planning to connect to a new, out-of-the-box, router for the initial configuration. This router allows you to connect using an Ethernet port, and you know that it has a Web interface. You have your laptop at hand. How do you proceed to successfully access the router? 

To get to the Web interface, you must first set a static address for the laptop that has the same network ID as the factory-default IP address of the router. To discover this address, you must read the documentation that came with the router. Then connect to the router, either with a crossover cable (if specified in the documentation), directly with a straight-through Ethernet cable (again, per the documentation), or by connecting them to the same switch. Open your browser and enter the IP address of the router; this should bring up the login screen for the router's configuration utility.

112. (p. 203) Define an Autonomous System. 

An Autonomous System (AS) is one or more networks governed by a single protocol with that AS. An AS sits at the top of the multitiered structure of the Internet.

113. (p. 202) Explain why neither version of RIP is practical for a large WAN. 

Both RIPv1 and RIPv2 have a problem with the time to convergence for large WANs, and both still have a limit of 15 hops.

114. (p. 208-209) Define EIGRP. 

Enhanced Interior Gateway Routing Protocol (EIGRP) is a hybrid Cisco-proprietary protocol that has aspects of both distance vector and link state protocols. It is gradually been replaced by non-proprietary IGP protocols, such as OSPF.

115. (p. 186) Define the "Tier One" backbone: 

The Tier One backbone is where the routers that make up the primary connections of the Internet reside.

116. (p. 198) Define a routing metric, and list four routing metrics. 

Routing tables contain criteria called a metric - a relative value that routers use when there is more than one route to another network. Metrics determine which route to use. Lower-value metrics are used first. Different routing protocols use different metrics and ways of calculating them. Metrics include: MTU, hop count, latency, bandwidth, and cost.

117. (p. 193) Define PAT. 

Port Address Translation is the most commonly used form of NAT. It handles one-to-many connections to the Internet from the internal network. It uses port numbers to map traffic from specific machines on the network by changing the private source address and port number to something usable on the Internet. The original address and port are recorded in the PAT translation table and swapped for a new one that is used on the Internet. The return traffic destined for the original host is "swapped" back through the table and sent to original machine.

118. (p. 218) In addition to the tracert and ping commands, what is another Windows utility that can be used to troubleshoot connections, and how does it work? 

Pathping is another Windows utility that can be used to troubleshoot connection issues, in addition to tracert and ping. This utility will ping each node on the route just like mtr, but instead of showing the results of each ping in real time, the pathping utility computes the performance over a set time, then shows you the summary after it has finished.

119. (p. 190) How does Cisco describe its Fast Ethernet interfaces? 

The term "fa0/0" is how Cisco describes Ethernet NICs in its device software. It is short for FastEthernet, which you may remember as being the common name for 100BaseTX.

120. (p. 211) From a security perspective, what is one of the first things that should be accomplished with a new router? 

Every brand of router tends to use the same default user names and password. Just about every Linksys router, for example, uses a blank user name and the password "admin." An admin who fails to change the default password is not properly securing the router. In addition to other configuration options an administrator should take before connecting a router to the network, changing the default password is one of the most important things they should accomplish.