CCNP 642-811 BCMSN Exam Certification Guide - Cisco press

526Appendix A: Answers to Chapter “Do I Know This Already?” Quizzes and Q&A Sections

11.d

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Q&A

1.When Cisco IOS Software is used on a Catalyst switch, the switch must perform routing. True or false?

Answer: False

2.What is the major difference between the IOS and CatOS command sets?

Cisco IOS Software uses the familiar router configuration commands and a hierarchy of configuration modes. CatOS uses “set” commands with no explicit configuration mode. Also, IOS configuration commands are not automatically saved across a power failure, whereas CatOS commands are. Cisco IOS Software also offers the ability to switch packets at Layer 3, whereas CatOS was never extended beyond Layer 2.

3.What switch command will enter privileged EXEC or “enable” mode on a Catalyst 4500? enable

4.Match these default command line prompts with their respective modes:

5.With the command line prompt testlab#, what command has been used to customize the prompt?

hostname testlab

6.The following commands have just been entered, assuming interface VLAN 10 did not previously exist:

interface vlan 10

ip address 192.168.199.10 255.255.255.0 no shutdown

528Appendix A: Answers to Chapter “Do I Know This Already?” Quizzes and Q&A Sections

11.When a Cisco Catalyst switch receives a CDP multicast frame, it relays it to neighboring switches. True or false?

Answer: False

12.Eight access layer switches connect to a central distribution layer switch using Gigabit Ethernet connections. Each connection is assigned to VLAN 1 so that no link is in trunking mode. On one of the access switches, how many neighboring switches will be shown by the show cdp neighbor gigabit 0/1?

Only one neighboring switch will be shown—the single distribution layer switch that is directly connected. CDP messages are not forwarded; rather, they are received and processed only by the neighboring switch. Because all eight access switches are connected by another switch, CDP messages don’t pass between them.

13.Which IOS image file is more recent—c3550-i5q3l2-mz.121-12c.EA1.bin or c3550-i9q3l2- mz.121-11c.EA1.bin?

c3550-i5q3l2-mz.121-12c.EA1.bin

14.A new switch has just been configured with 100 command lines from the console. You realize the need to save the new configuration and type copy start run. Where will your configuration be stored?

Unfortunately, the configuration you made might be lost or drastically changed. The startupconfig file will be copied into, or overlaid onto, the running-config. Any commands that are different in the startup-config will overwrite the commands you entered in the running-config. Because this is a new switch containing only the default commands, you could end up effectively overwriting your changes with the default values that the switch had when it powered up for the first time. The correct command should have been copy run start.

15.What command can you use to see what Cisco IOS Software version is currently running on a switch?

show version

16.Complete this command so that the output is displayed starting with the configuration for interface VLAN 100:

show run

show run | begin Vlan100

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17.The debug spanning-tree all command has been given from the EXEC mode command line. What commands can you use to stop or disable the debugging output?

no debug all

no debug spanning-tree all undebug all

18.What command can you use to verify CDP configuration on switch port GigabitEthernet 3/1? show cdp interface gigabit 3/1

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530 Appendix A: Answers to Chapter “Do I Know This Already?” Quizzes and Q&A Sections

Q&A

1.Put the following Ethernet standards in order of increasing bandwidth:

a.802.3z

b.802.3ae

c.802.3

d.802.3u

Answer: c, d, a, b

2.What benefits does switched Ethernet have over shared Ethernet?

Switched Ethernet ports receive dedicated bandwidth, have a reduced collision domain, and show increased performance due to segmentation or fewer users per port.

3.When a 10/100 Ethernet link is autonegotiating, which will be chosen if both stations can support the same capabilities—10BASE-T full duplex, 100BASE-TX half duplex, or 100BASE-TX full duplex?

100BASE-TX full duplex will be chosen because it has the highest autonegotiation priority and is common to both end stations.

4.How many pairs of copper wires does a 1000BASET connection need? Four pairs

5.A switch port is being configured as shown here. What command is needed next to set the port to full-duplex mode?

Switch(config)# interface fastethernet 0/13

Switch(config-if)#

Enter the command duplex full at the prompt.

6.If a full-duplex Gigabit Ethernet connection offers 2 Gbps throughput, can a single host send data at 2 Gbps?

No, a full-duplex Gigabit Ethernet connection allows only 1 Gbps simultaneously in each direction across the link.

7.Which GBIC would you use for a connection over multimode fiber (MMF)? You could use either a 1000BASE-SX or a 1000BASE-LX/LH.

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8.When might Long Reach Ethernet be a good candidate for a connection?

In a multitenant building, such as an office or apartment building, where existing Category 1, 2, or 3 wiring is already present for telephone services.

9.A Category 5 cable having only pins 1,2 and 3,6 has been installed and used for a Fast Ethernet link. Can this same cable be used for a migration to Gigabit Ethernet using 1000BASE-T GBICs, assuming the length is less than 100 meters?

No. 1000BASE-T requires all four pairs of wires to be present.

10.A Catalyst 3550 switch port has been configured for 100 Mbps full-duplex mode, but a link cannot be established. What are some commands that you could use to investigate and correct the problem?

To see the current state of one or more ports, you could use the show interface command. This would show the ports’ speed and duplex modes, as well as whether a link has been established. One reason the link is not established could be that the port is shut down or disabled. To enable the port, use the no shutdown interface configuration command. Because the port has been set to 100 Mbps full-duplex mode, it is possible that the end station can support only 10 Mbps at half duplex. Therefore, set the port for autonegotiate mode with the speed auto and duplex auto commands. Otherwise, you could set the port to a fixed speed and mode that would match the end station.

11. 10Gigabit Ethernet is backward-compatible with other forms of Ethernet at Layer 2 but not at Layer 1 .

12.What types of Ethernet are commonly used to connect geographically separate locations? Metro Ethernet, transported over facilities contracted from a service provider

13.What form of Metro Ethernet allows several enterprise VLANs to be transported between locations—TLS or DVS?

Directed VLAN Service (DVS)

14.What one switch command will select Fast Ethernet interfaces 4/1 through 48 for a common configuration?

interface range fastethernet 4/1 - 48

(Don’t forget spaces around the dash.)

532Appendix A: Answers to Chapter “Do I Know This Already?” Quizzes and Q&A Sections

15.What is a GBIC’s purpose?

A GBIC is used as a modular media-independent connection for Gigabit Ethernet. A switch with a GBIC port will accept GBIC modules that support various network media types. Changing network media cabling requires only a low-cost GBIC module change.

16.Suppose you need to apply several different common configurations to Fast Ethernet interfaces 3/1 through 12, 3/34, 3/48, and 5/14 through 48. What commands are needed to create an interface macro to accomplish this, and what command would apply the macro?

define interface-range mymacro fastethernet 3/1 – 12, fastethernet 3/34 – 48 , fastethernet 5/14 – 48 interface range macro mymacro

17.If a switch port is configured with the speed 100 and duplex full commands, what will happen if the PC connected to it is set for autonegotiated speed and duplex? Now reverse the roles (the switch will autonegotiate, but the PC won’t). What will happen?

When the PC attempts to autonegotiate the link settings, it will detect the switch port’s speed of 100 Mbps. However, the duplex cannot be detected without a two-way information exchange, so the PC will probably fall back to half duplex. The results are similar when the roles are reversed, as the switch will decide on 100 Mbps half duplex. In either case, a duplex mismatch will occur.

18.By default, what will a switch do if one of its ports has a serious error condition, and how can you tell when this has happened?

By default, every possible error condition is detected on every port. If any one of these conditions occurs, the port will be automatically shut down in the errdisable state. The show interface status err-disabled command shows a brief summary of all ports in the errdisable state.

19.What port speeds can you assign to a UTP Gigabit Ethernet switch port? Consider both 1000BASE-T GBIC and native RJ-45 copper switch module ports.

A 1000BASE-T GBIC is fixed at 1 Gbps, whereas switch modules with UTP Gigabit Ethernet ports can be 10 Mbps, 100 Mbps, or 1000 Mbps.

20.What command can you use to make sure that no switch ports are automatically shut down in an errdisable state for any reason?

Use the no errdisable detect cause all interface configuration command. Remember that all causes are enabled by default, so you must disable all causes first.

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21.Suppose you commonly find that switch ports are being shut down in errdisable due to users making their connections go up and down too often. Thinking this might be due to odd PC behavior, you would like to visit each user to troubleshoot the problem. However, this is a minor error and you don’t want to inconvenience the end users too much. What commands can you use to have the switch automatically reenable the ports after 10 minutes? Make sure a flapping link will be automatically recovered in this time frame.

errdisable recovery interval 600 errdisable recovery cause link-flap

22.Look at the following show interface output. Does the high number of collisions indicate a problem? Why or why not?

FastEthernet0/6 is up, line protocol is up

Hardware is Fast Ethernet, address is 000a.f4d2.5506 (bia 000a.f4d2.5506) Description: kelly-107-1d1,pc

MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec, reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set Keepalive set (10 sec)

Half-duplex, 10Mb/s

input flow-control is off, output flow-control is off ARP type: ARPA, ARP Timeout 04:00:00

Last input never, output 00:00:00, output hang never Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0 Queueing strategy: fifo

Output queue :0/40 (size/max)

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

1321140 packets input, 227738894 bytes, 0 no buffer Received 13786 broadcasts, 0 runts, 0 giants, 0 throttles 1 input errors, 1 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog, 42 multicast, 0 pause input

0 input packets with dribble condition detected

87798820 packets output, 2662785561 bytes, 1316 underruns

6 output errors, 406870 collisions, 3 interface resets

0 babbles, 0 late collision, 19458 deferred

0 lost carrier, 0 no carrier, 0 PAUSE output

1316 output buffer failures, 0 output buffers swapped out

Yes, this would probably be normal, considering that the interface is set for 10-Mbps half duplex. Collisions are to be expected on a link with shared bandwidth; in this case, the link is part of a collision domain. If the link were showing full duplex at any speed, collisions should never be detected.

534 Appendix A: Answers to Chapter “Do I Know This Already?” Quizzes and Q&A Sections

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Q&A

1.What is a VLAN? When is it used?

A VLAN is a group of devices on the same broadcast domain, such as a logical subnet or segment. VLANs can span switch ports, switches within a switch block, or closets and buildings. VLANs group users and devices into common workgroups across geographical areas. VLANs help provide segmentation, security, and problem isolation.

2.When a VLAN is configured on a Catalyst switch port, in how much of the campus network will the VLAN number be unique and significant?

The VLAN number will be significant in the local switch. If trunking is enabled, the VLAN number will be significant across the entire trunking domain. In other words, the VLAN will be transported to every switch that has a trunk link supporting that VLAN.

3.Name two types of VLANs in terms of spanning areas of the campus network. Local VLAN

End-to-end VLAN

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4.What switch commands configure Fast Ethernet port 4/11 for VLAN 2? interface fastethernet 4/11

switchport mode access switchport access vlan 2

5.Generally speaking, what must be configured (both switch and end user device) for a port-based VLAN?

The switch port

6.What is the default VLAN on all ports of a Catalyst switch? VLAN 1

7.What is a trunk link?

A trunk link is a connection between two switches that transports traffic from multiple VLANs. Each frame is identified with its source VLAN during its trip across the trunk link.

8.What methods of Ethernet VLAN frame identification can be used on a Catalyst switch trunk? 802.1Q

ISL

9.What is the difference between the two trunking methods? How many bytes are added to trunked frames for VLAN identification in each method?

ISL uses encapsulation and adds a 26-byte header and a 4-byte trailer. 802.1Q adds a 4-byte tag field within existing frames, without encapsulation.

10.What is the purpose of Dynamic Trunking Protocol (DTP)?

DTP allows negotiation of a common trunking method between endpoints of a trunk link.

11.What commands are needed to configure a Catalyst switch trunk port Gigabit 3/1 to transport only VLANs 100, 200 through 205, and 300 using IEEE 802.1Q? (Assume that trunking is enabled and active on the port already. Also, assume the interface gigabit 3/1 command has already been entered.)

switchport trunk allowed vlan 100, 200-205, 300