Chapter 12: Troubleshooting Ethernet LAN's Flashcards Preview

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Flashcards in Chapter 12: Troubleshooting Ethernet LAN's Deck (57)
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1

Which answers describe a good practice in applying good troubleshooting method- ologies? (Choose two answers.)
a. Perform problem isolation as fast as possible, including not slowing down to document your findings.
b. The last step in a good troubleshooting process should be to take action to resolve the root cause of the problem.
c. The last step in a good troubleshooting process should include monitoring the status to ensure that the problem is indeed solved and does not recur.
d. Each worker should know and use the escalation process when they cannot resolve a particular problem.

C,D

2

The output of the show interfaces status command on a 2960 switch shows interface Fa0/1 in a “disabled” state. Which of the following is true about interface Fa0/1? (Choose three answers.)
a. The interface is configured with the shutdown command.
b. The show interfaces fa0/1 command will list the interface with two status codes
of administratively down and line protocol down.
c. The show interfaces fa0/1 command will list the interface with two status codes of up and down.
d. The interface cannot currently be used to forward frames.
e. The interface can currently be used to forward frames.

A,B,D

3

Switch SW1 uses its Gigabit 0/1 interface to connect to switch SW2’s Gigabit 0/2 interface. SW2’s Gi0/2 interface is configured with the speed 1000 and duplex full commands. SW1 uses all defaults for interface configuration commands on its Gi0/1 interface. Which of the following are true about the link after it comes up? (Choose two answers.)
a. The link works at 1000 Mbps (1 Gbps).
b. SW1 attempts to run at 10 Mbps because SW2 has effectively disabled IEEE
standard autonegotiation.
c. The link runs at 1 Gbps, but SW1 uses half-duplex and SW2 uses full duplex.
d. Both switches use full duplex.

A,D

4

In the following line taken from a show interfaces fa0/1 command, which of the fol- lowing are true about the interface? (Choose two answers.)
Full-duplex, 100Mbps, media type is 10/100BaseTX
a. The speed was definitely configured with the speed 100 interface subcommand.
b. The speed might have been configured with the speed 100 interface
subcommand.
c. The duplex was definitely configured with the duplex full interface subcommand.
d. The duplex might have been configured with the duplex full interface subcommand.

B,D

5

Which of the following commands list the MAC address table entries for MAC addresses configured by port security? (Choose two answers.)
a. show mac address-table dynamic
b. show mac address-table
c. show mac address-table static
d. show mac address-table port-security

B,C

6

On a Cisco Catalyst switch, you issue a show mac address-table command. Which of the following answers list information you would likely see in most lines of output? (Choose two answers.)
a. A MAC address
b. An IP address
c. A VLAN ID
d. Type (broadcast, multicast, or unicast)

A,C

7

The show port-security interface f0/1 command lists a port status of secure-down. Which one of the following answers must be true about this interface at this time?
a. The show interface status command lists the interface status as connected.
b. The show interface status command lists the interface status as err-disabled.
c. The show port-security interface command could list a mode of shutdown or restrict, but not protect.
d. The show port-security interface command could list a violation counter value of 10.

B

8

The show interfaces g0/1 switchport command on SW1 shows the trunking status on a link connected to switch SW2. Based on the output, which of the following must be true on SW2’s port connected to this link?
SW1# show interfaces gigabit0/1 switchport
Name: Gi0/1
Switchport: Enabled Administrative Mode: trunk Operational Mode: trunk
a. The operational state per show interfaces switchport must be “trunk.”
b. The administrative state per show interfaces switchport must be “trunk.”
c. SW2 must use the switchport mode trunk configuration command on G0/2, or the link will not use trunking.
d. SW2 can use the switchport mode dynamic auto configuration command as one option to make the link use trunking.

D

9

Three steps in applying troubleshooting methodologies:

Problem isolation and documentation

Resolve or escalate

Verify or monitor

10

Four troubleshooting topics for the 105 exam.

1.Examining interface status and statistics
2.Analyzing where switches will forward frames
3.Analyzing port security
4.Analyzing VLANs and VLAN trunking

11

Which two commands list the two-code status named the line status and protocol status?

1. show interfaces
2.show interfaces description

12

The line status refers to which layer ?

Layer 1

13

The protocol status refers to which layer ?

Layer 2

14

Which command lists the interface status with a one word description that corresponds to the line/protocol description of the show interfaces command?

Show interfaces status

15

Name the line status,protocol status, and interface status associated with the following: The shutdown command is configured on the interface.

Line Status: Admin down

Protocol Status: down

Interface Status: disabled

16

Name the line status,protocol status, and interface status associated with the following: No cable; bad cable; wrong cable pinouts; speed mismatch; neighboring device is (a) powered off, (b) shutdown, or (c) error disabled.

Line Status: down

Protocol Status: down

Interface Status: notconnect

17

Name the line status,protocol status, and interface status associated with the following: Not expected on LAN switch physical interfaces.

Line Status: up

Protocol Status: down

Interface Status: notconnect

18

Name the line status,protocol status, and interface status associated with the following: Port security has disabled the interface.

Line Status: down

Protocol Status: down(err-disabled)

Interface Status: err-disabled

19

Name the line status,protocol status, and interface status associated with the following:The interface is working.

Line Status: up

Protocol Status: up

Interface Status: connected

20

With both configured, a switch or router disables the IEEE-standard autonegotiation process on that interface:

Speed int command
Duplex int command

21

commands list both the actual speed and duplex settings on an interface:

The show interfaces and show interfaces status commands

22

Which command implies how the switch determined the speed and duplex settings?

Show int status

23

When one device has disabled autonegotiation, and the other device uses autonegotiation, the device using autonegotia- tion chooses the default duplex setting based on the current speed. The defaults are as follows:

■ If the speed is not known through any means, use 10 Mbps, half duplex.
■ If the switch successfully senses the speed without IEEE autonegotiation, by just looking
at the signal on the cable:
■ If the speed is 10 or 100 Mbps, default to use half duplex.
■ If the speed is 1,000 Mbps, default to use full duplex.

24

Finding a duplex mismatch can be much more difficult than finding a speed mismatch, because:

if the duplex settings do not match on the ends of an Ethernet segment, the switch interface will still be in a connected (up/up) state.

25

To identify duplex mismatch problems:

check the duplex setting on each end of the link and watch for incrementing collision and late collision counters

26

How can you check for late collisions on a interface configured to half duplex?

keep repeating the show interfaces command, and if you see the late collisions counter incrementing on a half- duplex interface, you might have a duplex mismatch problem.

27

Summarize switch forwarding logic including the LAN switching features discussed in this book:

Step 1.
Process functions on the incoming interface, if the interface is currently in an up/up (connected) state, as follows:
A. If configured, apply port security logic to filter the frame as appropriate.
B. If the port is an access port,determine the interface’s accessVLAN.
C. If the port is a trunk, determine the frame’s tagged VLAN.

Step 2.
Make a forwarding decision. Look for the frame’s destination MAC address in the MAC address table, but only for entries in the VLAN identified in Step 1. If the destination MAC is...
A. Found (unicast), forward the frame out the only interface listed in the matched address table entry.
B. Not found(unicast),flood the frame out all other access ports(except the incoming port) in that same VLAN, plus out trunks that have not restricted the VLAN from that trunk (as discussed in Chapter 11, “Implementing Ethernet Virtual LANs,” as related to the show interfaces trunk command).
C. Broadcast, flood the frame, with the same rules as the previous step.

28

Which commands will identify the interfaces that have port security enabled?

1. Show running-config
2.Show port-security

29

The general process to find port security issues is as follows:

Step 1
Identify all interfaces on which port security is enabled (show running-config or show port-security)
Step 2
Determine whether a security violation is currently occurring based in part on the violation mode of the interface’s port security configuration, as follows:
A. shutdown: The interface will be in an err-disabled state, and the port security port status will be secure-down.
B. restrict:The interface will be in a connected state,the port security port status will be secure-up, but the show port-security interface command will show an incrementing violations counter.
C. protect: The interface will be in a connected state, and the show port-security interface command will not show an incrementing violations counter.

Step 3
In all cases, compare the port security configuration to the diagram and to the Last Source Address field in the output of the show port-security interface command.

30

To recover from an err-disabled state:

the interface must be shut down with the shutdown command, and then enabled with the no shutdown command