Chapter 12 - Troubleshooting Ethernet LANs Flashcards
Which answers describe a good practice in applying good troubleshooting methodologies?
(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 and D.
This question asks about a topic that, by nature, is subjective. Cisco does not dictate a particular predefined troubleshooting methodology. However, many good practices make good common sense and work in real networks. The incorrect answers to this question were chosen to be a bit obvious just to make the point about what Cisco does mention about troubleshooting methods in the exam topics, because this question takes those exam topics and builds in some common sense as applied to the exam topics.
One incorrect answer says to not slow down to document problems. This is contrary to one of the exam topics, and is certainly against good troubleshooting practices. Do problem isolation and record your findings.
Two answers state what the last step in the troubleshooting process should be, so one must be incorrect, possibly both (that is, only one step could be the last step). Resolving the problem is not the last step. After resolving the problem, the person working the problem should verify whether the problem is indeed solved, and possibly monitor the status for a period of time before considering the problem resolved.
The answer that mentions the escalation process basically defines a good process: If the engineer cannot resolve the problem, he should know how to escalate the problem to another engineer or manager, and he should indeed follow that process.
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, and D.
The disabled state in the show interfaces status command is the same as an “administratively down and down” state shown in the show interfaces command. The interface must be in a connected state (per the show interfaces status command) before the switch can send frames out the interface.
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 and D.
SW2 has effectively disabled IEEE standard autonegotiation by configuring both speed and duplex. However, Cisco switches can detect the speed used by the other device, even with autonegotiation turned off. Also, at 1 Gbps, the IEEE autonegotiation standard says to use full duplex. If the duplex setting cannot be negotiated, both ends use 1 Gbps, full duplex.
In the following line taken from a show interfaces fa0/1 command, which of the following 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 and D.
The show interfaces command lists the actual speed and duplex setting, but it does not imply anything about how the settings were configured or negotiated. The show interfaces status command lists a prefix of a- in front of the speed and duplex setting to imply that the setting was autonegotiated, leaving off this prefix if the setting was configured.
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 and C.
IOS adds MAC addresses configured by the port security feature as static MAC addresses, so they do not show up in the output of the show mac address-table dynamic command. show mac address-table port-security is not a valid command.
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 and C.
The show mac address-table command lists all entries in the switch’s MAC address table, including dynamically learned and statically defined addresses. From left to right, the output lists the VLAN ID, the MAC address, the type (static or dynamic), and the associated ports (out which frames sent to the listed address will be forwarded by this switch).
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.
The question states that the port security status is secure-shutdown. This state is used only by the shutdown port security mode, and when used, it means that the interface has been placed into an err-disabled state. Those facts explain why the correct answer is correct and two of the incorrect answers are incorrect.
The incorrect answer that mentions the violation counter is incorrect because in shutdown mode, the counter no longer increments once the interface is placed into secure-shutdown mode, and resets to 0 once the interface is reset with the shutdown and then no shutdown commands.
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.
The show interface switchport command lists a switch’s configured value of the switchport mode command as the administrative mode, telling us that SW1 uses the switchport mode trunk configuration command. The operation state shows the current working state (trunk). Of the four answers, one incorrect answer claims that SW2’s operational state must also be “trunk”; however, one switch can use trunking while the other does not. Another answer claims that the administrative mode must be “trunk,” which basically means that the switchport mode trunk command must be used. However, SW2 has a few other configuration options that would work, like the switchport mode dynamic desirable and switchport mode dynamic auto commands, with the correct answer referring to one of those commands (the switchport mode dynamic auto command).
