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This page has 7 EtherChannel and LACP Scenarios scenario questions for the 350-401 exam, each with detailed explanations and wrong-answer analysis.

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Read the full scenario before looking at the answer options. Identify the constraint or requirement in the scenario, then eliminate options that are generally true but wrong for this specific case. Scenario questions reward careful reading over pattern matching.

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EtherChannel and LACP Scenarios

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scenario questions

350-401

exam code

Cisco

vendor

Scenario guide

How to approach etherchannel and lacp scenarios

EtherChannel bundles multiple physical links into a single logical port-channel. The CCNA tests LACP vs PAgP vs static EtherChannel, the mode combinations that form a channel, and common configuration errors. These appear as configuration tasks and troubleshooting scenarios.

Quick answer

EtherChannel questions usually test whether bundled links have matching settings and whether LACP, PAgP or static mode is being used correctly.

LACP, PAgP and static EtherChannel modes.

Matching speed, duplex, VLAN, trunk and native VLAN settings.

Port-channel interface behaviour.

Why a link fails to join an EtherChannel bundle.

Practice scenarios

Question 1mediummultiple choice

Read the full EtherChannel explanation →

A network engineer runs the following command on Switch SW1:

SW1# show etherchannel summary

Flags: D - down P - bundled in port-channel I - stand-alone s - suspended H - Hot-standby (LACP only) R - Layer3 S - Layer2 U - in use N - not in use, no aggregation f - failed to allocate aggregator

M - not in use, minimum links not met u - unsuitable for bundling w - waiting to be aggregated d - default port

Number of channel-groups in use: 1 Number of aggregators: 1

Group Port-channel Protocol Ports ------+-------------+-----------+-------------------------------------------- 1 Po1(SU) LACP Gi0/1(P) Gi0/2(P) Gi0/3(D)

Based on this output, what can be concluded?

A
The EtherChannel is using PAgP.
Why it fails: The EtherChannel is using PAgP. The output clearly shows the EtherChannel protocol as LACP (Link Aggregation Control Protocol, IEEE 802.3ad), not PAgP (Port Aggregation Protocol, Cisco proprietary). In the 'show etherchannel summary' output, the 'Protocol' column would list LACP, confirming that PAgP is not in use. PAgP and LACP are mutually exclusive, so this option is factually incorrect.
B
Port Gi0/3 is bundled in the channel.
Why it fails: Port Gi0/3 is bundled in the channel. In 'show etherchannel summary', each member port is assigned a flag: 'P' means the port is bundled and actively participating in the channel, while 'D' means the port is down or administratively down. Gi0/3 shows the flag 'D', not 'P', so it is not part of the active EtherChannel bundle. Only ports with the 'P' flag are actively forwarding traffic.
C
The port-channel is a Layer 3 interface.
Why it fails: The port-channel is a Layer 3 interface. The output identifies the port-channel's layer type via a flag on the logical interface: 'S' signifies a Layer 2 port-channel, whereas 'R' would denote a Layer 3 routed port-channel. Since the flag shown is 'S', the EtherChannel is operating at Layer 2, making this statement incorrect. A Layer 3 port-channel would require an 'R' flag and an IP address configured on the logical interface.
D
The EtherChannel has two active member links.
The EtherChannel has two active member links. The 'P' flag appears on both Gi0/1 and Gi0/2, indicating that exactly two physical interfaces are bundled into the port-channel and are actively forwarding traffic. Since no other ports display the 'P' flag, the EtherChannel is active with two member links. Other ports, such as Gi0/3, show 'D' and are not part of the operational bundle, confirming the two-link count.

Full breakdown with real-world context →

Question 2mediummultiple choice

Open the full VLAN trunking answer →

Consider this configuration:

interface Port-channel1
 switchport mode trunk
 switchport trunk native vlan 999

interface GigabitEthernet0/1
 switchport mode trunk
 switchport trunk native vlan 999
 channel-group 1 mode active

interface GigabitEthernet0/2
 switchport mode trunk
 switchport trunk native vlan 999
 channel-group 1 mode active

What is the effect of the 'switchport trunk native vlan 999' command on the EtherChannel?

A
The EtherChannel will drop all untagged frames because the native VLAN is not in the allowed list.
Why it fails: The native VLAN is the VLAN assigned to untagged frames on an 802.1Q trunk, and it does not need to be listed in the allowed VLAN list for those frames to be forwarded. The EtherChannel will not drop untagged frames merely because the native VLAN is absent from the allowed list; instead, untagged traffic is associated with the configured native VLAN. A mismatch between the allowed list and the native VLAN would only affect tagged traffic in that VLAN, not untagged frames.
B
The EtherChannel will use VLAN 999 as the native VLAN, and any untagged frames will be associated with VLAN 999.
Correct: When the native VLAN is configured as 999 on the EtherChannel, the port-channel treats all untagged frames as belonging to VLAN 999. This is standard 802.1Q trunk behavior: untagged frames are placed into the native VLAN, and in this case the native VLAN is explicitly set to 999 rather than the default VLAN 1. Both ends of the EtherChannel must agree on the native VLAN value to avoid misconfiguration, and here that consistency is maintained.
C
The EtherChannel will not form because the native VLAN must be the same across all interfaces, which it is.
Why it fails: The statement is incorrect because the native VLAN on all interfaces is already consistent (VLAN 999), which satisfies the requirement for forming an EtherChannel. The native VLAN does need to match across all member links, but since it does match, the EtherChannel will form normally. Merely having a consistent native VLAN is a prerequisite, not a barrier, so the claim that the channel will not form is false.
D
The EtherChannel will form but the native VLAN will be ignored on the port-channel.
Why it fails: The port-channel does not ignore the native VLAN; instead, it inherits the native VLAN configuration from the physical member interfaces when the logical interface is created. Once the EtherChannel is operational, the port-channel uses VLAN 999 as its native VLAN, so any untagged frames arriving on the port-channel are associated with that VLAN. The native VLAN is fully functional on the port-channel and must be the same on both sides of the channel to prevent traffic misclassification.

Full breakdown with real-world context →

Question 3mediummultiple choice

Read the full EtherChannel explanation →

A network engineer is troubleshooting an EtherChannel between two Cisco switches. The show etherchannel 1 port-channel command shows the port-channel is up, but traffic is not load-balanced evenly. The engineer notices that all traffic is using only one link. The physical ports are all configured identically. What is the most likely cause?

A
The load-balancing method is set to src-mac, and the traffic is from multiple MAC addresses.
Why it fails: With the src-mac load-balancing algorithm, the EtherChannel hash is computed solely from the source MAC address. If traffic originates from multiple distinct MAC addresses, those frames produce different hash values and are distributed across different member links, not all on one link. Therefore, this scenario cannot explain why all traffic is traversing a single port.
B
The load-balancing method is set to src-dst-ip, and all traffic is between the same two IP addresses.
The src-dst-ip method hashes both the source and destination IP addresses together to select an egress link. When every packet between two IP endpoints is going between the same pair, the hash output is identical for each packet, so the deterministic hash always maps to the same member port. This is exactly the condition that forces all traffic onto a single link, even if multiple flows exist between those IPs.
C
The physical ports have different speeds.
Why it fails: If member ports operated at different speeds, the EtherChannel would not form correctly; Cisco switches require all ports in a channel to have matching speed and duplex settings. Ports with mismatched speeds would be excluded from the bundle or the channel would fail, rather than the channel staying up and simply sending all traffic on the fastest port. Since the port-channel is operational, speed mismatch is not the underlying cause.
D
The port-channel is configured with 'lacp fast-switchover'.
Why it fails: The 'lacp fast-switchover' feature reduces the time needed to move traffic to a hot-standby port when an active port fails; it does not alter the load-balancing hash or influence how traffic is initially distributed across links. It is a failover optimization for LACP EtherChannels, not a mechanism that changes steady-state forwarding behavior. Hence, it cannot be responsible for single-link congestion.

Full breakdown with real-world context →

Question 4hardmultiple choice

Read the full EtherChannel explanation →

A network engineer runs the following command on Switch SW7:

SW7# show interfaces port-channel 1

Port-channel1 is up, line protocol is up (connected) Hardware is EtherChannel, address is aaaa.bbbb.cccc (bia aaaa.bbbb.cccc) Description: Link to Core Internet address is 192.168.1.1/30 MTU 1500 bytes, BW 2000000 Kbit/sec, DLY 10 usec, reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec) Full-duplex, 1000Mb/s, link type is auto, media type is unknown input flow-control is off, output flow-control is unsupported ARP type: ARPA, ARP Timeout 04:00:00 Last input 00:00:00, output 00:00:00, output hang never Last clearing of "show interface" counters never Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0 Queueing strategy: fifo Output queue: 0/40 (size/max) 5 minute input rate 1000 bits/sec, 2 packets/sec 5 minute output rate 500 bits/sec, 1 packets/sec 12345 packets input, 1234567 bytes, 0 no buffer Received 0 broadcasts (0 IP multicasts) 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored 0 watchdog, 0 multicast, 0 pause input 0 input packets with dribble condition detected 67890 packets output, 9876543 bytes, 0 underruns 0 output errors, 0 collisions, 2 interface resets 0 unknown protocol drops 0 babbles, 0 late collision, 0 deferred 0 lost carrier, 0 no carrier, 0 pause output 0 output buffer failures, 0 output buffers swapped out

Based on this output, what can be concluded?

A
The port-channel is a Layer 2 interface because it has an IP address.
Why it fails: The statement is incorrect because an IP address on a port-channel interface does not make it Layer 2; rather, it designates the interface as a Layer 3 (routed) port. In Cisco IOS, assigning an IP address to a port-channel creates a routed interface, whereas a Layer 2 port-channel requires the 'switchport' command and operates as a VLAN trunk or access port, without an IP address. Therefore, the presence of an IP address is evidence of Layer 3 operation, not Layer 2.
B
The bandwidth of 2 Gbps suggests that two 1 Gbps links are aggregated.
The bandwidth of 2 Gbps (shown as 2000000 Kbit/sec) correctly suggests that two 1 Gbps links are aggregated into this EtherChannel. In an EtherChannel, the logical interface bandwidth is the sum of the bandwidths of all member links, and with two full-duplex 1 Gbps member ports, the combined bandwidth becomes 2 Gbps. This aligns with the expected output for a two-member PortChannel and confirms the aggregation is active.
C
The interface is experiencing input errors due to CRC errors.
Why it fails: The claim that the interface is experiencing input errors due to CRC errors is false because the provided output shows '0 input errors' and '0 CRC' counters. CRC errors, such as those caused by physical layer noise or faulty cabling, would appear as a non-zero value in the input error and CRC error fields. Since both counters are zero, there is no evidence of any input error or CRC-related problem on this port-channel.
D
The port-channel is operating at half-duplex.
Why it fails: The statement that the port-channel is operating at half-duplex is directly contradicted by the interface output, which explicitly shows 'Full-duplex'. EtherChannel member links must operate in full-duplex mode to avoid collisions and ensure proper aggregation, and the output confirms that this requirement is satisfied. A half-duplex operation would be a misconfiguration and would appear as 'Half-duplex' in the show output, which is not the case here.

Full breakdown with real-world context →

Question 5easymultiple choice

Read the full EtherChannel explanation →

Which LACP mode must be configured on at least one side of an EtherChannel for the channel to establish?

A
Active
Active is the correct choice because LACP Active mode proactively initiates the EtherChannel negotiation by sending LACP packets to the peer. It successfully forms a channel with a peer configured in either Active or Passive mode, making it the preferred mode for dynamic link aggregation in standards-based (IEEE 802.3ad) environments.
B
Passive
Why it fails: Passive is incorrect in this context because it represents the non-initiating side of LACP negotiation. A port in Passive mode only waits for and responds to incoming LACP packets; it never sends its own initiation frames. Consequently, if both ends are set to Passive, the EtherChannel will never form, so it cannot satisfy the requirement to actively negotiate the link.
C
Desirable
Why it fails: Desirable is not a valid LACP mode; rather, it belongs to Cisco's proprietary PAgP (Port Aggregation Protocol). While PAgP Desirable does actively initiate negotiation, it uses a different protocol and frame format than LACP. Since the question specifically targets LACP behavior, choosing Desirable indicates a confusion between PAgP's 'desirable/auto' and LACP's 'active/passive' mode naming schemes.
D
On
Why it fails: On is incorrect because it denotes a static EtherChannel configuration that bypasses any negotiation protocol, neither LACP nor PAgP. Placing a port in On mode forcefully bundles it into a channel without exchanging control frames, which can lead to bridging loops if the peer is not similarly configured. Since the scenario requires LACP-based negotiation, On fails because it does not initiate (or participate in) LACP signaling.

Full breakdown with real-world context →

Question 6mediumdrag order

Read the full EtherChannel explanation →

Drag and drop the steps of configuring a Layer 2 EtherChannel using PAgP into the correct order, from first to last.

Drag or tap steps into the slots.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Question 7mediummatching

Read the full EtherChannel explanation →

Drag and drop each EtherChannel port state on the left to its matching description on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts

Matches

Port is actively forwarding traffic in the EtherChannel

Port is active but not part of any EtherChannel

Port is administratively down or error-disabled in the channel

A
bundled: Port is actively forwarding traffic in the EtherChannel
Correct: This describes a bundled port that actively forwards traffic.
B
stand-alone: Port is active but not part of any EtherChannel
Correct: This describes a stand-alone port that is active but not in a channel.
C
suspended: Port is administratively down or error-disabled in the channel
Correct: This describes a suspended port that is down or error-disabled.
D
bundled: Port is a member of the channel and forwarding
Why it fails: Incorrect: This is a duplicate of the bundled state. While the description is valid, only P1 is the intended match.
E
stand-alone: Port operates as a regular switch port
Why it fails: Incorrect: This is a duplicate of the stand-alone state. While the description is valid, only P2 is the intended match.

Full breakdown with real-world context →

These 350-401 practice questions are part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style 350-401 questions with detailed explanations, topic-based practice, mock exams, readiness tracking, and study analytics.

EtherChannel and LACP Scenarios

How to approach etherchannel and lacp scenarios

Quick answer

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Practice scenarios

Which LACP mode must be configured on at least one side of an EtherChannel for the channel to establish?

Drag and drop the steps of configuring a Layer 2 EtherChannel using PAgP into the correct order, from first to last.

Drag and drop each EtherChannel port state on the left to its matching description on the right.