CCNA Troubleshooting Questions 2

By | July 26, 2017

This is an Updated CCNA exam questions (2016). You might come across different IP addressing, Port allocation and Configurations.

As usual, take time and read through the question so as to clearly understand what the question is all about.

Note: This network troubleshooting question are used for demonstration only, you might find a slightly different IP addressing, Port allocation in the real CCNA exam. But it all works the same way if you could just grasp the technique.

I suggest you use packet tracer for practice.




Question 1

Refer to the exhibit.

How should the FastEthernet0/1 ports on the switches that are shown in the exhibit be configured to allow connectivity between all devices?
A. The ports only need to be connected by a crossover cable.

B. Switch1(config)# interface fastethernet 0/1
Switch1(config-if)# switchport mode trunk

C. Switch1(config)# interface fastethernet 0/1
Switch1(config-if)# switchport mode access
Switch1(config-if)# switchport access vlan 1

D. Switch1(config)# interface fastethernet 0/1
Switch1(config-if)# switchport mode trunk
Switch1(config-if)# switchport trunk vlan 1
Switch1(config-if)# switchport trunk vlan 10
Switch1(config-if)# switchport trunk vlan 20

Answer: B

Explanation:

To enable multiple VLANs to communicate between switches, the connection between the switches must be a trunk link. The switchport mode trunk command is all that is needed, the individual VLANs should not be listed on that trunk interface.

Question 2

What parameter can be different on ports within an EtherChannel?

A. speed
B. DTP negotiation settings
C. trunk encapsulation
D. duplex
Answer: B

Explanation:

For an EtherChannel to come up, the speed, duplex, and the trunk encapsulation must be the same on each end.

Question 3

Refer to the exhibit.

Which two statements are true about interVLAN routing in the topology that is shown in the exhibit above? (Choose two.)
A. Host E and host F use the same IP gateway address.
B. Router1 and Switch2 should be connected via a crossover cable.
C. Router1 will not play a role in communications between host A and host D.
D. The FastEthernet 0/0 interface on Router1 must be configured with subinterfaces.
E. Router1 needs more LAN interfaces to accommodate the VLANs that are shown in the exhibit.
F. The FastEthernet 0/0 interface on Router1 and the FastEthernet 0/1 interface on Switch2 trunk ports must be configured using the same encapsulation type.

Answer : D,F

Explanation:

To enable multiple VLANs to connect to a single physical interface on a Cisco router, the interface must be configured with subinterfaces, one for each VLAN. This is known as the router on a stick configuration.

Also, for any trunk to be formed, both ends of the trunk must agree on the encapsulation type, so each one must be configured for 802.1q or ISL.




Question 4

Refer to the exhibit.

Which WAN protocol is being used?

A. ATM
B. HDLC
C. Frame Relay
D. PPP
Answer: C

Explanation:

According to the information provided in the exhibit, we can verify that the data link protocol used in this network is the Frame Relay protocol. LMI enq sent

Question 5

Refer to the exhibit.

Switch port FastEthernet 0/24 on ALSwitch1 will be used to create an IEEE 802.1Q compliant trunk to another switch. Based on the output shown, what is the reason the trunk does not form, even though the proper cabling has been attached?

A. VLANs have not been created yet.
B. An IP address must be configured for the port.
C. The port is currently configured for access mode.
D. The correct encapsulation type has not been configured.
E. The “no shutdown” command has not been entered for the port.
Answer: C

Explanation:

According to the output shown the switchport (layer 2 Switching) is enabled and the port is in access mode. The port should be configured as a trunk port, not an access port, by using the following command:

(Config-if)#switchport mode trunk.

Question 6

Refer to the exhibit.

Which two statements are true of the interfaces on Switch1? (Choose two.)

A. Multiple devices are connected directly to FastEthernet0/1.
B. A hub is connected directly to FastEthernet0/5.
C. FastEthernet0/1 is connected to a host with multiple network interface cards.
D. FastEthernet0/5 has statically assigned MAC addresses.
E. FastEthernet0/1 is configured as a trunk link.
F. Interface FastEthernet0/2 has been disabled.
Answer: B, E

Explanation:

Carefully observe the information provided by the output;  you will notice that Fa0/1 is connected to Switch2, seven MAC addresses correspond to Fa0/1, and these MAC are on different VLAN. From this, we can confirm that Fa0/1 is the trunk interface.

Also from the info provided by the show cdp neighbors we can verify that the  F0/5 interface corresponds to two MAC addresses in the same VLAN. This shows that Fa0/5 is connected to a Hub.

In summary, there are multiple MAC addresses from different VLANs attached to the FastEthernet 0/1 interface. Only trunks are able to pass information from devices in multiple VLANs.

Question 7

Refer to the network shown in the exhibit.

Which option contains both the potential networking problem and the protocol or setting
that should be used to prevent the problem?

A. routing loops, hold down timers
B. switching loops, split horizon
C. routing loops, split horizon
D. switching loops, VTP
E. routing loops, STP
F. switching loops, STP
Answer: F

Explanation:

The Spanning-Tree Protocol (STP) prevents loops from being formed when switches or bridges are interconnected via multiple paths. Spanning-Tree Protocol implements the 802.1D IEEE algorithm by exchanging BPDU messages with other switches to detect

Spanning-Tree Protocol implements the 802.1D IEEE algorithm by exchanging BPDU messages with other switches to detect loops and then removes the loop by shutting down selected bridge interfaces. This algorithm guarantees that there is one and only one active path between two network devices.

This algorithm guarantees that there is one and only one active path between two network devices.




Question 8

At which layer of the OSI model is RSTP used to prevent loops?

A. physical
B. data link
C. network
D. transport
Answer: B

Explanation:

RSTP and STP operate on switches and are based on the exchange of Bridge Protocol Data Units (BPDUs) between switches. One of the most important fields in BPDUs is the Bridge Priority in which the MAC address is used to select the Root Bridge -> RSTP operates at Layer 2 Data Link layer ->.

Question 9

Refer to the exhibit.

What set of commands was configured on interface Fa0/3 to produce the given output?

A. interface FastEthernet 0/3 channel-group 1 mode desirable switchport trunk encapsulation dot1q switchport         mode trunk
B. interface FastEthernet 0/3 channel-group 2 mode passive switchport trunk encapsulation dot1q switchport         mode  trunk
C. interface FastEthernet 0/3 channel-group 2 mode active switchport trunk encapsulation dot1q switchport              mode trunk
D. interface FastEthernet 0/3 channel-group 2 mode on switchport trunk encapsulation dot1q switchport mode        trunk

Answer: B

Explanation:

Based on the output shown, the configured channel group number was 2 and the mode used was passive, the answer is self-explanatory.

Question 10

Refer to the exhibit.

Given this output for SwitchC, what should the network administrator’s next action be?

A. Check the trunk encapsulation mode for SwitchC’s fa0/1 port.
B. Check the duplex mode for SwitchC’s fa0/1 port.
C. Check the duplex mode for SwitchA’s fa0/2 port.
D. Check the trunk encapsulation mode for SwitchA’s fa0/2 port.
Answer: C

Explanation:

Here we can verify that this port is configured for full duplex, so the next step would be to check the duplex setting of the port on the other switch. A mismatched trunk encapsulation would not result in input errors and CRC errors.

Question 11

Three switches are connected to one another via trunk ports. Assuming the default switch configuration, which switch is elected as the root bridge for the spanning-tree instance of VLAN 1?

A. the switch with the highest MAC address
B. the switch with the lowest MAC address
C. the switch with the highest IP address
D. the switch with the lowest IP address
Answer: B

Explanation:

Each switch on a network will have a Bridge ID Priority value (BID).

This BID is a combination of a default priority value and the switch’s MAC address, with the priority value listed first. The lowest BID will win the election process. E.g, if a Cisco switch has the default priority value of 32768 and a MAC address of 11-22-33-44-55-66, the BID would be 32768:11-22-33-44-55-66. Therefore, if the switch priority is left at the default, the MAC address is the deciding factor in the root bridge election.