Do I Know This Already Quiz

1. Which of the following commands is valid for the configuration of IP address 10.1.1.1, mask 255.255.255.0?

Answer: C

2. Which of the following must be true before Cisco IOS Software adds a connected route to the routing table?

Answer: A and E. The router adds the subnet number of the directly connected interface to the routing table after the IP address is configured. The interface must be operational before the route is added.

3. Which of the following represents the same ideas as mask 255.255.240.0?

Answer: C. The answers all use prefix notation, which represents the subnet mask by stating the number of binary 1s in the mask.

4. What command brings up an interface that previously was administratively disabled? Answer: A. shutdown disables the interface, and no shutdown brings it back up.

5. Imagine that a PC is attached to the same Ethernet as a router. The PC makes a DNS request for host name Fred, and the PC gets a reply showing IP address 10.1.1.1. What command could be issued on the router to list the information learned in that DNS request and reply?

Answer: D. The show hosts command lists the host name configured in the router or names learned by the router from the DNS as a result of a command on the router using the name. The router does not learn about names as a result of DNS requests from an end user.

6. Imagine that a neighboring router's host name is Hannah. Which of these commands could tell you information about the IOS version on Hannah, without Telnetting to Hannah?

Answer: H and I. CDP discovers information about neighbors. show cdp gives you several options that display more or less information, depending on the parameters used.

7. What CDP command(s) could identify the model of hardware of a neighbor? Answer: F, G, and H

8. Imagine that you used a ping command successfully. What messages would have been sent by the ping command?

Answer: B

9. Imagine that you just erased all the configuration on a router and reloaded it. To configure the router to use a DNS at IP address 10.1.1.1, which of the following commands is required?

Answer: A

10. Imagine that you just logged in to the console of router R1 and then Telnetted to R2. What must you type to suspend your Telnet connection, going back to R1?

Answer: C

Q&A

Create a minimal configuration enabling IP on each interface on a 2501 router (two serial, one Ethernet). The NIC assigned you network 8.0.0.0. Your boss says that you need, at most, 200 hosts per subnet. You decide against using VLSM. Your boss also says to plan your subnets so that you can have as many subnets as possible rather than allow for larger subnets later. When choosing the actual IP address values and subnet numbers, you decide to start with the lowest numerical values. Assume that point-to-point serial links will be attached to this router.

interface ethernet 0

ip address 8.0.1.1 255.255.255.0

interface serial 0

ip address 8.0.2.1 255.255.255.0

interface serial 1

ip address 8.0.3.1 255.255.255.0

Answer: The zero subnet was not used in this solution. If desired, the ip subnet-zero global command could have been used, enabling subnet 8.0.0.0/24 as well as subnets 8.0.1.0/24 and 8.0.2.0/24 to be used as the three subnets in the configuration.

2. In the previous question, what would be the IP subnet of the link attached to serial 0? If another user wanted to answer the same question but did not have the enable password, what command(s) might provide this router's addresses and subnets?

Answer: The attached subnet is 8.0.2.0, 255.255.255.0. The show interface, show ip interface, and show ip interface brief commands would supply this information, as would show ip route. The show ip route command would show the actual subnet number instead of the address of the interface.

3. What must be done to make the output of the show ip route command list subnet masks in decimal format instead of prefixes? In what mode would you use the command?

Answer: You must use the terminal ip netmask-format decimal command in enable mode.

4. What are the differences between the clock rate and bandwidth commands?

Answer: clock rate sets the physical (Layer 1) actual transmission rate, in bits per second, and only when a DCE cable has been plugged into that interface. The bandwidth command, with units of kbps, does not affect Layer 1 transmission rates. Instead, it is used by Cisco IOS Software as its understanding of the Layer 1 rate, for purposes such as calculation of routing protocol metrics.

5. Compare and contrast the commands used to set the enable, console, and telnet passwords on a router.

Answer: The password command sets the console and telnet password. When used as a line console 0 subcommand, it sets the console password; under line vty 0 4, it sets the telnet password. The enable password can be set with the enable password or enable secret commands, with the enable secret password taking precedence if both are configured.

6. In the output of show ip route, when a C shows up in the left side of the output on a line for a particular route, what does that mean?

Answer: C means "connected." This means that the route was learned by this router because it has an operational interface that is connected directly to that subnet.

7. Define the term prefix notation. Give two examples.

Answer: The representation of a subnet mask with a slash character (/), followed by a number that represents the number of binary 1s in the mask. For example, /16 means the same thing as 255.255.0.0, and /22 means the same thing as 255.255.252.0.

8. What does ICMP stand for? To which OSI layer would you consider this protocol to apply most closely?

Answer: Internet Control Message Protocol. ICMP is considered a Layer 3 protocol because it is used for control and management of IP.

9. Identify two methods to tell a router to ask for name resolution from two different name servers.

ip name-server 1.1.1.1 2.2.2.2 or ip name-server 1.1.1.1 ip name-server 2.2.2.2

Answer: Both methods tell the router to first try the name server at 1.1.1.1 and then try the name server at 2.2.2.2.

10. What keyboard sequence suspends a Telnet session in a Cisco router? Answer: Ctrl-Shift-6, followed by x.

11. What two commands, and what part the command output, tells you which suspended Telnet connection will be reconnected if you just press the Enter key, without any characters typed on the command line?

Answer: show sessions and where. Both commands supply the same information. The suspended session with an asterisk in the left side of the output line designates the session to which you would be connected if you just pressed Return, with no characters on the command line.

12. Imagine that you typed a ping command and got 5 "!" back. What type of messages were sent through the network? Be as specific as possible.

Answer: ICMP echo request messages were sent by the ping command, with the remote host replying with five ICMP echo reply messages.

13. How do you make a router not ask for DNS resolution from a name server? Answer: By using the no ip domain-lookup global configuration command.

14. Imagine that you are just logged in at the console of R1, and you Telnet to routers R2, R3, and R4 in succession, but you suspended your Telnet connection each time—in other words, all three Telnet connections go from R1 to the other three routers, respectively. What options do you have for reconnecting to R2?

Answer: You can use the resume 1 command or just use the 1 command.

15. Imagine that you are just logged in at the console of R1, and you Telnet to routers R2, R3, and R4 in succession, but you suspended your Telnet connection each time—in other words, all three Telnet connections go from R1 to the other three routers, respectively. What options do you have for reconnecting to R4?

Answer: You can use the resume 3 command or just use the 3 command. Or, you can simply press Enter, which resumes your connection to the last suspended Telnet connection—in this case, R4.

16. List the five key pieces of information that can be gathered using CDP, as mentioned in the chapter.

Answer: Device identifier, address list, port identifier, capabilities list, and platform.

17. Imagine a network with Switch1, connected to Router1, with a point-to-point serial link to Router2, which, in turn, is connected to Switch2. Assuming that you are logged into R1, what commands could be used to find the IP addresses of Router2 and Switch1 without logging in to either device?

Answer: On Router1, you could use either the show cdp neighbor detail command or the show cdp entry command. Both commands list IP addresses of the neighboring devices, assuming that CDP is up and working.

18. Imagine that a network with Switch1 is connected to Router1, with a point-to-point serial link to Router2, which, in turn, is connected to Switch2. You can log in only to Switch1. Which of the other devices could Switch1 learn about using CDP? Why?

Answer: Switch1 could learn about only Router1 because CDP learns information about only devices that are connected to the same data link.

19. What command lists a brief one-line description of CDP information about each neighbor?

Answer: The show cdp neighbor command.

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