New CCNA EtherChannel Question and Answers with Explanation

By | September 24, 2017

This is an Updated  CCNA Ethernet exam question ( 2016). You might see a different IP addressing, VLAN configuration and Port allocation Configurations.
As usual, take time to read through the question so as to clearly understand what Cisco want you to do.
Note: This Etherchannel questions are used for demonstrat ion only.

Question 1
Standard industrialized protocol of Etherchannel?
A. LACP
B. PAGP
C. PRP
D. REP
Answer: A

Question 2
Which statement is true regarding the Port Aggregation Protocol?
A. Configuration changes made on the port-channel interface apply to all physical ports assigned to the                       port-channel interface.
B. Configuration changes made on a physical port that is a member of a port-channel interface apply to the port-      channel interface.
C. Configuration changes are not permitted with Port Aggregation Protocol; instead, the standardized Link                Aggregation Control Protocol should be used if configuration changes are required.
D. The physical port must first be disassociated from the port-channel interface before any configuration changes can be made.

Answer: A
Explanation
The port-channel interface represents the whole bundle and all the configurations on this interface are equally affects to all physical ports that are assigned to this logical interface.
Note: when you manually create port-channel logical interface when configuring Layer 3 EtherChannels.
This forces the port-channel logical interface to be created automatically.
An example of configuring Layer 3 EtherChannels with port-channel interfaces:

Note: The “no switchport” command is required to change the interface from layer2 to layer3 mode.

Question 3
What is the status of port-channel if LACP is misconfigured?
A. Forwarding
B. Enabled
C. Disabled
D. Errdisabled
Answer: C

Question 4

Refer to the exhibit. LACP has been configured on Switch1 as shown. Which is the correct command set to configure LACP on Switch2?

A.
Switch2# configure terminal
Switch2(config)# interface range gigabitethernet3/1 -2
Switch2(config-if)# channel-group 5 mode auto

B.
Switch2# configure terminal
Switch2(config)# interface range gigabitethemet3/1 -2
Switch2(config-if)# channel-group 5 mode passive

C.
Switch2# configure terminal
Switch2(config)# interface range gigabitethernet3/1 -2
Switch2(config-if)# channel-group 5 mode desirable

D.
Switch2# configure terminal
Switch2(config)# interface range gigabitethernet3/1 -2
Switch2(config-if)# channel-group 5 mode on

Answer: B

Explanation

LACP trunking supports four modes of operation:
* On: The link aggregation is forced to be formed without any LACP negotiation. In other words, the switch will              neither send the LACP packet nor process any incoming LACP packet. This is similar to the on state for                  PAgP.
* Off: The link aggregation will not be formed. We do not send or understand the LACP packet. This is similar                  to  the off state for PAgP.
* Passive: The switch does not initiate the channel, but does understand incoming LACP packets. The peer (in                         active   state) initiates negotiation (by sending out an LACP packet) which we receive and reply to,                         eventually forming the aggregation channel with the peer. This is similar to the auto mode in PAgP.
* Active: We are willing to form an aggregate link, and initiate the negotiation. The link aggregate will be                              formed if the other end is running in LACP active or passive mode. This is similar to the desirable mode of PAgP.

(Reference: http://www.cisco.com/en/US/tech/tk389/tk213/technologies_configuration_example09186a0080094470.shtml)



Question 5
What is the result of entering the command “port-channel load-balance src-dst-ip” on an EtherChannel link?
A. Packets are distributed across the ports in the channel based on both the source and destination MAC addresses.
B. Packets are distributed across the ports in the channel based on both the source and destination IP addresses.
C. Packets are balanced across the ports in the channel based first on the source MAC address, then on the destination MAC address, then on the IP address.
D. Packets are distributed across the access ports in the channel based first on the source IP address and then the destination IP addresses.

Answer: B
Explanation
The syntax of configuring load balancing on a Cisco switch is:
Switch(config)# port-channel load-balance method
By default, the “src-dst-ip” (source and destination IP address) method is used for Layer 3 switching.
The “port-channel load-balance src-dst-ip” command uses a pair of source & destination IP address to select the port to send traffic to.

Question 6
Refer to the exhibit. Which statement is true about the display of the command “show pagp 1 neighbor” command?

A. STP packets are sent out the Gi0/1 interface only.
B. STP packets are sent out both the Gi0/1 and Gi0/2 interfaces.
C. CDP packets are sent out the Gi0/1 interface only.
D. CDP packets are sent out the Gi0/2 interface only.

Answer: A
Explanation
Both DTP and CDP send and receive packets over all the physical interfaces in the EtherChannel network while STP always chooses the first operational port in an EtherChannel bundle

Question 7
Refer to the exhibit.
base of the information being displayed by the show commands, which two EtherChannel statements are true? (Choose two)

A. Interfaces FastEthernet 0/1 and 0/2 have been configured with the channel-group 1 mode desirable command.
B. Interfaces FastEthernet 0/3 and 0/4 have been configured with the no switchport command.
C. Interface Port-Channels 1 and 2 have been assigned IP addresses with the ip address commands.
D. Port-Channels 1 and 2 are providing two 400 Mbps EtherChannels.
E. Port-Channels 1 and 2 are capable of combining up to 8 FastEthernet ports to provide full-duplex bandwidth of up to 16 Gbps between
a switch and another switch or host.
F. Switch SW1 has been configured with a Layer 3 EtherChannel.

Answer: A D
Explanation
A is chosen in this case but, its known that two ports Fa0/1 & Fa0/2 of Sw1 can use the “channel-group 1 mode auto” command while the peer ports
use the “channel-group 1 mode desirable” command.
Di is chosen here because there are 2 ports in each group totalling to 4 Ethernet ports. i.e 100Mbps per port = 400Mbps in full duplex

Question 8
Refer to the exhibit. The command switchport mode access is issued on interface FastEthernet0/13 on switch CAT1. What will be the result?

A. The command will be rejected by the switch.
B. Interfaces FastEthernet0/12 and FastEthemet0/13 will no longer be bundled.
C. Dynamic Trunking Protocol will be turned off on interfaces FastEthernet0/12 and FastEthemet0/13.
D. Interfaces FastEthernet0/12 and FastEthernet0/13 will only allow traffic from the native VLAN.
E. Interfaces FastEthernet0/12 and FastEthernet0/13 will continue to pass traffic for VLANs 88,100,360.

Answer: B
Explanation
The default channel protocol in Cisco switches is Port Aggregation Protocol (PAgP). PAgP groups the interfaces with the same speed, duplex mode, native VLAN, VLAN range, and trunking status and type. After grouping the links into an EtherChannel, PAgP adds the group to the spanning tree as a single switch port.
An interface in the on mode that is added to a port channel is forced to have the same characteristics as the already existing on mode interfaces in the channel (applied for both PAgP & LACP). So if we configure “switchport mode access” on Fa0/13, this interface will no longer be bundled with Fa0/14.
(Reference: http://www.cisco.com/en/US/docs/switches/lan/catalyst3550/software/release/12.1_14_ea1/configuration/guide/swethchl.html#wpxref12539)




Question 9
Which three statements are true of the Link Aggregation Control Protocol (LACP)? (Choose three)
A. LACP is used to connect to non-Cisco devices.
B. LACP packets are sent with the command channel-group 1 mode desirable.
C. LACP packets are sent with the command channel-group 1 mode active.
D. Standby interfaces should be configured with a higher priority.
E. Standby interfaces should be configured with a lower priority.

Answer: A C D
Explanation
LACP is part of the IEEE specification 802.3ad so that it can be used on non-Cisco devices
A is correct.
With mode “active”, the switch will send LACP packets, initiates negotiations with remote ports and willing to form a port-channel if it receives a response
C is correct.
LACP uses the port priority with the port number to form the port identifier.
The port priority determines which ports should be put in standby mode when there is a hardware limitation that prevents all compatible ports from aggregating.
The valid range is from 1 to 65535. The higher the number, the lower the priority so standby interfaces should be configured with a higher priority.
D is correct.

Question 10
Refer to the exhibit. What does the command channel-group 1 mode desirable do?

Interface FastEthernet 0/13
Channel-group 1 mode desirable

A. enables LACP unconditionally
B. enables PAgP only if a PAgP device is detected
C. enables PAgP unconditionally
D. enables Etherchannel only
E. enables LACP only if a LACP device is detected

Answer: C
Explanation
For a starter, “desirable” is one of the mode of PAgP, not LACP.
enable PAgP unconditionally” enables that port  send PAgP packets to form an EtherChannel port (initiate negotiations with other ports).
A channel is formed with another port group in either desirable or auto mode.
Note:
Mode “auto” enables PAgP only if a PAgP device is detected and mode “on” forces the port to form a channel.

Question 11
Which statement best describes implementing a Layer 3 EtherChannel?
A. EtherChannel is a Layer 2 and not a Layer 3 feature.
B. Implementation requires switchport mode trunk and matching parameters between switches.
C. Implementation requires disabling switchport mode.
D. A Layer 3 address is assigned to the channel-group interface.

Answer: C
Explanation
By default, ports on a multilayer switch (MLS) runs in Layer 2 mode. A port must be configured as a routing port before it is configured as a Layer 3 EtherChannel .

Question 12
After an EtherChannel is configured between two Cisco switches, interface port channel 1 is in the down/down state.
Switch A is configured with channel-group 1 mode active, while Switch B is configured with channel-group 1 mode desirable.
Why is the EtherChannel bundle not working?

A. The switches are using mismatched EtherChannel negotiation modes.
B. The switch ports are not configured in trunking mode.
C. LACP priority must be configured on both switches.
D. The channel group identifier must be different for Switch A and Switch B.
Answer A

Question 13
Refer to the exhibit. While troubleshooting a switch, you executed the “show interface port-channel 1 etherchannel” command and it returned this output.
Which information is provided by the Load value?

A. the percentage of use of the link
B. the preference of the link
C. the session count of the link
D. the number source-destination pairs on the link
Answer: D

Question 14
What parameter can be different on ports within an EtherChannel?
A. speed
B. DTP negotiation settings
C. trunk encapsulation
D. duplex
Answer: B