CCNA Etherchannel Questions

MCQhard

Two switches should form an LACP EtherChannel. One side is configured passive, and the other side is also passive. What is the most likely result?

A.The EtherChannel is unlikely to form because neither side initiates LACP negotiation.

B.The EtherChannel always forms because passive mode is stronger than active mode.

C.The link becomes a routed port automatically.

D.Both switches delete the port-channel configuration.

AnswerA

In LACP, the 'passive' mode waits for an incoming LACP PDU and never sends one on its own. Since both switches are configured as passive, neither end transmits the initial LACP negotiation frames required to detect the peer and agree on link parameters, so the EtherChannel remains in a down or unattached state. LACP requires at least one side to be 'active' to begin the exchange.

Why this answer

If both sides are passive, the EtherChannel is unlikely to form because passive mode waits for the other side to initiate LACP negotiation. In plain language, both switches are listening, but neither is actively starting the conversation. Because neither side takes the active role, the bundle normally stays down or unformed unless one side is changed to active.

This is a classic LACP negotiation question. It reinforces the difference between valid pairings such as active/active or active/passive and the passive/passive pairing that usually fails to initiate negotiation.

Exam trap

Remember, passive mode waits for the other side to initiate. Ensure at least one side is active to form an EtherChannel.

Why the other options are wrong

Passive mode does not initiate LACP negotiation; it only responds to incoming LACP packets. Active mode is the one that actively sends LACP packets. Therefore, passive mode is not stronger than active mode.

LACP configuration does not change the interface type; it only bundles multiple physical links into a logical EtherChannel. The interface remains a Layer 2 or Layer 3 port based on its configuration, not a routed port automatically.

Passive mode does not cause the switch to delete the port-channel configuration. The configuration remains, but the EtherChannel will not come up because no LACP negotiation occurs.

Practice this question →

PBQmedium

You are connected to SW1 via the console. SW1 is a Layer 2 switch with two redundant links to SW2 (G0/1 and G0/2). The network administrator wants to use both links for load balancing and redundancy by configuring EtherChannel. You need to configure a Layer 2 EtherChannel using LACP on both switches. The port-channel should be in VLAN 1.

Network Topology

Hints

•LACP uses modes active or passive; both sides must be active or one active and one passive.
•The physical interfaces must have the same configuration before being added to the port-channel.
•The port-channel interface inherits the configuration applied to it, not the physical interfaces.

A.interface port-channel 1 switchport mode access switchport access vlan 1 interface range GigabitEthernet0/1-2 channel-group 1 mode active

B.interface port-channel 1 switchport mode trunk switchport trunk allowed vlan 1 interface range g0/1-2 channel-group 1 mode desirable

C.interface port-channel 1 switchport mode access switchport access vlan 1 interface range g0/1-2 channel-group 1 mode passive

D.interface port-channel 1 switchport mode access switchport access vlan 1 interface g0/1 channel-group 1 mode active interface g0/2 channel-group 2 mode active

AnswerA

solution

! SW1
interface GigabitEthernet0/1
channel-group 1 mode active
interface GigabitEthernet0/2
channel-group 1 mode active
interface Port-channel1
switchport mode access
switchport access vlan 1

! SW2
interface GigabitEthernet0/1
channel-group 1 mode active
interface GigabitEthernet0/2
channel-group 1 mode active
interface Port-channel1
switchport mode access
switchport access vlan 1

Why this answer

EtherChannel bundles multiple physical links into a single logical link for load balancing and redundancy. LACP (mode active) negotiates the bundle automatically. The port-channel interface must be configured with the desired switchport settings.

Exam trap

Be careful to distinguish between LACP modes (active/passive) and PAgP modes (desirable/auto). Also, remember that all interfaces in an EtherChannel must use the same channel-group number and have consistent switchport settings. A common mistake is to configure trunk when an access port is needed, or to use passive on both sides, which prevents the bundle from forming.

Why the other options are wrong

Uses PAgP mode 'desirable' instead of LACP mode 'active'. Additionally, configuring trunk is unnecessary for a single VLAN access port.

Using 'passive' on both sides would prevent the EtherChannel from forming because neither side sends LACP packets.

Using different channel-group numbers creates separate EtherChannels, not a single bundle. Both interfaces must be in the same channel-group to form one logical link.

MCQmedium

What is a common requirement for interfaces to successfully bundle into an EtherChannel?

A.All member interfaces must use matching speed, duplex, and trunk/access settings

B.Each interface must belong to a different VLAN

C.Only odd-numbered switch ports can be bundled

D.Each interface must have a different STP path cost

AnswerA

All member interfaces must have matching physical and logical characteristics to be eligible for EtherChannel bundling. This includes identical speed and duplex settings, because protocols like LACP and PAgP verify these parameters during negotiation and will not form a bundle if they differ. Additionally, each interface must be configured with the same operational mode—either access or trunk—with consistent native and allowed VLANs, so that the aggregated link behaves as a single port.

Why this answer

EtherChannel members must have compatible operational and administrative settings, including speed, duplex, and switchport mode.

Exam trap

Remember that EtherChannel is concerned with Layer 2 settings like speed and duplex, not Layer 3 settings like IP addresses.

Why the other options are wrong

EtherChannel does not require interfaces to be in different VLANs; in fact, all member interfaces must have the same VLAN configuration (either all access ports in the same VLAN or all trunk ports with the same allowed VLAN list). Placing interfaces in different VLANs would violate the consistency requirement and prevent bundling.

Port numbering (odd or even) has no bearing on EtherChannel eligibility; any physical ports on a switch can be bundled as long as they meet the configuration consistency requirements. The restriction is based on hardware capabilities, not port numbers.

STP path cost is a per-interface value used by Spanning Tree Protocol to determine the best path to the root bridge; it is not a requirement for EtherChannel bundling. In fact, when interfaces are bundled, STP treats the EtherChannel as a single logical link, and all member interfaces share the same STP state.

Practice this question →

PBQhard

You are connected to SW1. Configure an LACP EtherChannel between SW1 and SW2 using interfaces GigabitEthernet0/1 and GigabitEthernet0/2. The port-channel interface must be configured as a trunk allowing VLANs 10, 20, and 30. Currently, the channel is not forming due to a mismatch in speed/duplex and VLAN configuration on SW2. Troubleshoot and resolve the issue so that the EtherChannel comes up as a Layer 2 trunk.

Network Topology

Hints

•Check the speed and duplex settings on SW2's physical interfaces.
•Compare the allowed VLAN list on SW2's physical interfaces to the port-channel trunk.
•Use 'show etherchannel summary' to see if ports are bundled or down.

A.On SW2, configure interfaces GigabitEthernet0/1 and 0/2 with speed 1000, duplex full, and on the port-channel interface, set allowed VLANs to 10,20,30.

B.On SW2, configure interfaces GigabitEthernet0/1 and 0/2 with speed 100, duplex half, and on the port-channel interface, set allowed VLANs to 10,20,30.

C.On SW2, configure interfaces GigabitEthernet0/1 and 0/2 with speed 1000, duplex full, and on the port-channel interface, set allowed VLANs to 10,20.

D.On SW2, configure interfaces GigabitEthernet0/1 and 0/2 with speed 1000, duplex full, and on the port-channel interface, set allowed VLANs to 1-4094.

AnswerA

solution

! SW2
interface gigabitEthernet0/1
speed 1000
duplex full
switchport trunk allowed vlan 10,20,30
interface gigabitEthernet0/2
speed 1000
duplex full
switchport trunk allowed vlan 10,20,30

Why this answer

The EtherChannel is not forming because SW2's interfaces have speed 100 and duplex half, while SW1's interfaces have speed 1000 and duplex full. Additionally, the allowed VLANs on SW2's trunk must include VLAN 30, and this should be configured on the port-channel interface, not the physical interfaces. To fix, on SW2, set the speed to 1000 and duplex to full on Gi0/1 and Gi0/2, then on the port-channel interface, configure allowed VLANs 10,20,30.

After these changes, the channel will come up as a Layer 2 trunk.

Exam trap

The exam trap is that candidates may focus solely on the speed/duplex mismatch and forget to verify the VLAN allowed list on the trunk. Also, they might incorrectly try to match by lowering SW1's settings instead of raising SW2's.

Why the other options are wrong

The specific factual error is that LACP requires all member interfaces to have identical speed and duplex settings; changing SW2 to 100/half does not match SW1's 1000/full.

The specific factual error is that the trunk must allow all required VLANs; omitting VLAN 30 violates the requirement.

The specific factual error is that the configuration does not match the requirement to allow only VLANs 10, 20, and 30; it allows all VLANs instead.

Practice this question →

MCQhard

Two switches are bundled with LACP, but only one physical link is forwarding traffic in the port-channel. What is the most likely reason?

A.One member interface has a trunk configuration mismatch

B.LACP requires exactly one active and one passive side only

C.STP blocks all but one interface inside every EtherChannel

D.EtherChannel cannot be used on trunk ports

AnswerA

When LACP negotiates a channel, all selected member interfaces must share identical Layer 2 properties, including encapsulation, native VLAN, and the allowed VLAN list. If one physical link's trunk parameters differ—for example, it permits a different VLAN set or uses a different native VLAN—that port is placed in a suspended or individual state and omitted from the port-channel. The mismatch is detectable with 'show etherchannel summary', where the offending link appears as 'S' or 'I' rather than bundled.

Why this answer

For an EtherChannel to form correctly, the member interfaces must match on key settings such as speed, duplex, trunking, and allowed VLAN list. A mismatch keeps one link from bundling even if LACP is enabled on both sides.

Exam trap

Be careful not to confuse individual link issues with overall port-channel configuration problems. Ensure all settings match across member interfaces.

Why the other options are wrong

LACP supports active-active mode where both sides are configured as active, which is a common and valid configuration. The statement that LACP requires exactly one active and one passive side is incorrect; active-passive is just one possible combination.

STP treats the entire EtherChannel as a single logical interface, so it does not block individual member links. STP will only block the port-channel itself if there is a loop, but it does not block all but one interface inside the channel.

EtherChannel is commonly used on trunk ports to increase bandwidth and provide redundancy between switches. There is no restriction that prevents EtherChannel from being used on trunk ports; in fact, it is a best practice for inter-switch links.

Practice this question →

MCQhard

A network engineer is configuring an EtherChannel between two switches. After applying the configuration, the port-channel fails to form. What is the most likely reason?

A.The member links use different switchport modes, so the channel cannot form correctly.

B.LACP requires both interfaces to use different channel-group numbers.

C.The interfaces must both be configured for PPP.

D.The bundle fails because BGP is not enabled on the switch.

AnswerA

For an EtherChannel to form, all member interfaces must share an identical configuration, including speed, duplex, VLAN membership, and critically the switchport mode. If one interface is configured as an access port while another is set to trunk, the channel negotiation sees a mismatch in the allowed VLAN set and tagging behavior, preventing the bundle from coming up. This is a common cause of an EtherChannel failing to form even when LACP is enabled on both sides, because the compatibility checks are strict.

Why this answer

The port-channel is not forming because the two member interfaces are not configured consistently. In practical terms, EtherChannel requires important characteristics to align across candidate member links. Here, one interface is a trunk and the other is configured as an access port, so the channel cannot be built cleanly.

This is a classic EtherChannel consistency problem. The protocol alone is not enough if the member-link settings disagree.

Exam trap

Always verify interface configurations for consistency when troubleshooting EtherChannel issues.

Why the other options are wrong

LACP requires that all member interfaces in the same port-channel use the same channel-group number. Using different numbers would place them in separate bundles, preventing the intended aggregation.

PPP is a Layer 2 encapsulation used on serial links, not on Ethernet switch ports. EtherChannel on Cisco switches uses Ethernet frames, and PPP is irrelevant to the configuration of port-channels.

BGP is a routing protocol that operates at Layer 3 and is not required for EtherChannel formation. EtherChannel is a Layer 2 technology that bundles physical links into a single logical link, independent of any routing protocol.

Practice this question →

MCQhard

An EtherChannel between SW1 and SW2 is not forming. The technician runs the show etherchannel summary command on both switches and sees that all configured interfaces are in the 'I' (stand-alone) state. Both switches have their interfaces configured with channel-group 1 mode active. What should the technician check next?

A.Verify that both switches are using the same EtherChannel protocol (LACP or PAgP).

B.Check that the speed and duplex settings match on all member interfaces.

C.Check for a VLAN mismatch on the member interfaces (e.g., mismatched native VLAN or allowed VLAN list).

D.Determine whether Spanning Tree Protocol is blocking one of the ports.

AnswerC

LACP requires that all member ports have identical VLAN configurations (switchport mode, allowed VLANs, native VLAN). A mismatch in any of these parameters keeps the ports in stand-alone state. Since the protocol is already confirmed as LACP, verifying VLAN consistency is the most appropriate next step.

Why this answer

When both switches are configured with channel-group 1 mode active, they are using LACP (active/active). The 'I' (stand-alone) state indicates the ports are not forming an EtherChannel despite LACP being enabled. A VLAN mismatch—such as differing native VLANs or allowed VLAN lists—can prevent LACP from successfully negotiating the bundle, as the control plane sees a Layer 2 inconsistency and keeps the ports in stand-alone mode.

Exam trap

Cisco often tests the misconception that the 'I' (stand-alone) state always indicates a physical or protocol mismatch, when in fact it frequently points to Layer 2 configuration inconsistencies like VLAN mismatches that prevent LACP from completing negotiation.

Why the other options are wrong

Assuming that a protocol mismatch might exist without checking the existing configuration first.

Prioritizing a Layer 1 check over a Layer 2 parameter that must be identical for EtherChannel to bundle.

Confusing STP port states with EtherChannel negotiation states.

Practice this question →

MCQhard

A network engineer configures an EtherChannel between two Cisco switches SW1 and SW2 using LACP. After configuration, hosts connected to SW1 report intermittent connectivity to hosts on SW2. The engineer checks the EtherChannel status and sees that the trunk is up but only allows VLAN 1, while the hosts communicate across VLANs 10 and 20. Which command should the engineer apply to both switches to resolve the issue?

A.channel-group 1 mode active

B.switchport trunk allowed vlan 1,10,20

C.lacp rate fast

D.switchport mode trunk

AnswerB

This command ensures that all member ports of the EtherChannel have the same VLAN list. Inconsistent allowed VLANs across member ports can cause traffic to be dropped intermittently. Applying this to all member interfaces on both switches resolves the issue.

Why this answer

The output shows the EtherChannel is up but only VLAN 1 is allowed on the trunk, while the hosts on SW1 and SW2 communicate across VLANs 10 and 20. Applying 'switchport trunk allowed vlan 1,10,20' on both switches ensures all necessary VLANs are permitted over the EtherChannel, resolving the intermittent connectivity caused by dropped traffic for VLANs 10 and 20.

Exam trap

The trap here is that candidates assume the EtherChannel is fully functional once it shows as up/up, overlooking that the trunk's VLAN allowed list must match on both sides to pass traffic for all required VLANs.

Why the other options are wrong

The ports are already configured with LACP active mode, as indicated by the protocol being LACP and the ports being bundled. Reapplying this command does not address the root cause of intermittent connectivity, which is likely due to VLAN mismatch.

The 'lacp rate fast' command changes the LACP packet transmission rate to every second, which is used for faster failure detection. It does not affect VLAN consistency or cause intermittent connectivity; the issue is likely due to VLAN mismatch, not LACP rate.

The ports are already configured as trunk ports (the Po1 is Layer2 and trunking is implied). Reapplying 'switchport mode trunk' does not address the VLAN inconsistency that causes intermittent connectivity.

Practice this question →

Multi-Selectmedium

Which TWO statements correctly describe EtherChannel configuration and verification with LACP?

Select 2 answers

A.LACP uses the modes 'active' and 'passive' to negotiate an EtherChannel.

B.LACP uses the modes 'desirable' and 'auto' to negotiate an EtherChannel.

C.The command 'show etherchannel summary' displays the status of each port-channel as SU (in use) or SD (shutdown).

D.The command 'show etherchannel summary' displays the status of each port-channel as UP or DOWN.

E.LACP 'active' mode can only form an EtherChannel with another interface in 'active' mode.

AnswersA, C

LACP's negotiation uses 'active' and 'passive' modes: an interface in active mode sends LACP PDUs to initiate channel formation, while a passive interface only replies when it receives those PDUs. A working EtherChannel requires at least one side to be active, since two passive interfaces will never begin negotiation. This is analogous to PAgP's desirable/auto pair but is standardized under IEEE 802.3ad.

Why this answer

LACP (IEEE 802.3ad) defines two negotiation modes: 'active' (sends LACP frames and initiates negotiation) and 'passive' (responds only to received LACP frames). An EtherChannel forms only when at least one side is in 'active' mode; two 'passive' sides will never negotiate. Option C is correct because the 'show etherchannel summary' command displays the port-channel status as 'SU' (in use, Layer 2) or 'SD' (administratively down/shutdown), not simply 'UP' or 'DOWN'.

Exam trap

Cisco often tests the distinction between LACP modes ('active'/'passive') and PAgP modes ('desirable'/'auto'), and the trap here is that candidates confuse the proprietary PAgP terms with the standards-based LACP terms, or assume 'show etherchannel summary' shows simple UP/DOWN like interface status.

Why the other options are wrong

The modes 'desirable' and 'auto' are used by PAgP (Cisco proprietary), not LACP. LACP uses 'active' and 'passive' modes for negotiation.

The 'show etherchannel summary' command does not display 'UP' or 'DOWN' in plain text; it uses two-letter codes like SU (Layer 2 up), SD (shutdown), etc. This is a common misinterpretation of the output format.

LACP 'active' mode can form an EtherChannel with either 'active' or 'passive' mode. If both sides are passive, the channel will not form because neither initiates negotiation.

Practice this question →

Drag & Dropmedium

Drag and drop the following steps into the correct order to configure an LACP EtherChannel on two Cisco switches using active mode.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

Why this order

First create the logical port-channel interface and configure its properties, then assign physical interfaces to it using channel-group with active mode to initiate LACP negotiation.

Exam trap

Cisco exams often test the correct order of EtherChannel configuration: always create the port-channel interface first. Also, distinguish between LACP modes (active/passive) and PAgP modes (desirable/auto).

Practice this question →

PBQhard

You are connected to SW1. Configure LACP EtherChannel between SW1 and SW2 using interfaces GigabitEthernet0/1 and GigabitEthernet0/2. Ensure the channel forms and passes traffic for VLAN 10. Troubleshoot and fix any issues preventing the channel from coming up.

Network Topology

Hints

•Check the speed and duplex settings on both member interfaces.
•Verify that the port-channel interface and member ports are both Layer2 or both Layer3.
•Ensure LACP mode is active on at least one side to initiate negotiation.

A.Configure speed 1000 and duplex full on Gi0/2, change port-channel 1 to switchport mode trunk with allowed vlan 10, and set both Gi0/1 and Gi0/2 to channel-group 1 mode active.

B.Configure speed 1000 and duplex full on Gi0/2, change port-channel 1 to no switchport, and set both Gi0/1 and Gi0/2 to channel-group 1 mode passive.

C.Configure speed 100 and duplex half on Gi0/1 to match Gi0/2, change port-channel 1 to switchport mode trunk with allowed vlan 10, and set both Gi0/1 and Gi0/2 to channel-group 1 mode active.

D.Configure speed 1000 and duplex full on Gi0/2, change port-channel 1 to switchport mode access with access vlan 10, and set both Gi0/1 and Gi0/2 to channel-group 1 mode desirable.

AnswerA

solution

! SW1
interface GigabitEthernet0/2
speed 1000
duplex full
channel-group 1 mode active
exit
interface GigabitEthernet0/1
channel-group 1 mode active
exit
interface Port-channel1
switchport
switchport mode trunk
switchport trunk allowed vlan 10
no ip address
end

Why this answer

The EtherChannel is not forming because of multiple mismatches: speed (1000 vs 100), duplex (full vs half), and the port-channel interface is configured as Layer3 (no switchport) while the member ports are Layer2 (switchport mode trunk). First, correct the speed and duplex on Gi0/2 to match Gi0/1 (speed 1000, duplex full). Then change the port-channel to switchport mode trunk and set the allowed VLAN.

Finally, change the LACP mode on both interfaces to 'active' to initiate negotiation. After these changes, the channel should come up.

Exam trap

Watch for mismatches in speed, duplex, and Layer2/Layer3 configuration between member ports and the port-channel interface. Also, ensure LACP mode is active on at least one side to initiate negotiation.

Why the other options are wrong

The specific factual error: The port-channel interface must match the Layer2 configuration of member ports; using no switchport creates a Layer3 interface that cannot trunk VLANs. Additionally, passive mode requires an active partner to form the channel.

The specific factual error: Speed and duplex should be consistent across all member links, but the correct resolution is to correct the misconfigured interface (Gi0/2) to match the working one (Gi0/1), not vice versa.

The specific factual error: Access mode cannot carry multiple VLANs; trunk mode is required for VLAN 10. Additionally, desirable is a PAgP keyword, not LACP. LACP uses active or passive.

Practice this question →

Multi-Selectmedium

Which THREE statements correctly describe the behavior of LACP modes in an EtherChannel configuration?

Select 3 answers

A.Active mode will not send LACP packets unless the peer is also in active mode.

B.Passive mode will only respond to LACP packets and will not initiate negotiation.

C.Passive mode cannot form an EtherChannel with another passive mode interface.

D.Active mode will initiate LACP negotiation by sending LACP packets.

E.Both active and passive modes are supported in PAgP.

AnswersB, C, D

Passive mode in LACP operates entirely reactively: it never sends LACPDUs on its own, but it listens for incoming LACPDUs and responds only after receiving a valid negotiation request. This behavior restricts passive mode to forming channels only with active peers, as no negotiation is possible until an active-side packet arrives. The interface essentially acknowledges and follows the negotiation led by the active side.

Why this answer

B is correct because passive mode interfaces only respond to LACP packets and never initiate negotiation. C is correct because two passive interfaces will both wait for the other to initiate, so no LACP packets are sent and the EtherChannel never forms. D is correct because active mode interfaces actively send LACP packets to initiate negotiation with either an active or passive peer.

A is incorrect: active mode sends LACP packets regardless of the peer’s mode; it can form a channel with passive just as well as with active. E is incorrect because PAgP supports only desirable and auto modes, not LACP’s active/passive modes; PAgP and LACP are separate protocols.

Exam trap

A common mistake is thinking active mode requires the peer to also be active, but active can form with either active or passive, while passive–passive pairs never negotiate.

Why the other options are wrong

Active mode sends LACP packets unconditionally; it does not require the peer to be active and will negotiate with a passive peer.

PAgP uses desirable and auto modes, not the LACP active/passive modes; these modes are specific to LACP.

Practice this question →

PBQmedium

You are connected to SW1 via the console. SW1 is a Layer 2 switch with two links to SW2: G0/1 and G0/2. The administrator wants to combine these two links into an EtherChannel using LACP. Configure an EtherChannel on SW1 for these ports and verify.

Hints

•EtherChannel requires a port-channel interface and channel-group configuration on member ports.
•Use mode active for LACP.

A.interface range g0/1-2 channel-group 1 mode active

B.interface range g0/1-2 channel-group 1 mode desirable

C.interface g0/1 channel-group 1 mode active interface g0/2 channel-group 1 mode passive

D.interface port-channel 1 channel-group 1 mode active

AnswerA

solution

! SW1
interface port-channel 1
interface range GigabitEthernet0/1-2
channel-group 1 mode active

Why this answer

It applies the LACP 'active' mode to both interfaces in the range, which will dynamically negotiate an EtherChannel with the peer. Option B uses PAgP 'desirable' mode, which is Cisco proprietary and not LACP, failing the requirement for LACP. Option C mixes LACP modes (active on one interface and passive on the other); both member ports must use the same mode (either active/active or passive/passive) to form a channel.

Option D attempts to configure the 'channel-group' command on the port-channel interface itself, but this command must be applied to the physical interfaces, not the logical port-channel.

Exam trap

Remember that LACP uses 'active' and 'passive' modes, while PAgP uses 'desirable' and 'auto'. Also, the 'channel-group' command is applied on physical interfaces, not on the port-channel interface. Both ports in the channel must use the same mode on the same switch.

Why the other options are wrong

The specific factual error is that 'desirable' is a PAgP mode, not LACP. LACP uses 'active' or 'passive'.

The specific factual error is that LACP requires both ends to be in compatible modes (active-active or active-passive), but on the same switch, both ports should use the same mode for the same channel group.

The specific factual error is that 'channel-group' is a physical interface command, not a port-channel interface command. The port-channel interface is used for logical configuration (e.g., trunking) after the channel is formed.

PBQhard

You are connected to SW1. An EtherChannel between SW1 and SW2 using LACP must be established on interfaces GigabitEthernet0/1 and GigabitEthernet0/2. Currently, the channel is not forming. Inspect the provided configuration and output, then apply the necessary commands on SW1 to resolve the issue and bring up the Port-Channel interface.

Network Topology

Hints

•Check the duplex and speed settings on both member interfaces on SW1.
•Verify that the native VLAN (or access VLAN if not trunking) is identical on all bundled ports.
•Ensure both sides use compatible LACP modes (active/active or active/passive).

A.Configure both interfaces with speed 1000, duplex full, and switchport access vlan 1.

B.Change the LACP mode on SW1's Gi0/2 from active to passive.

C.Configure both interfaces with speed 100, duplex half, and switchport access vlan 10.

D.Remove the switchport access vlan command from both interfaces and configure them as trunk ports with native vlan 1.

AnswerA

solution

! SW1
interface gigabitEthernet 0/2
speed 1000
duplex full
switchport access vlan 1
end

Why this answer

The EtherChannel failed because the two member interfaces on SW1 have mismatched speed (Gi0/1: 1000 Mbps, Gi0/2: 100 Mbps) and duplex (Gi0/1: full, Gi0/2: half), and their native VLANs differ (Gi0/1: VLAN 1, Gi0/2: VLAN 10). LACP requires all bundled ports to have identical speed, duplex, and VLAN configuration. To fix, on SW1 configure both interfaces with consistent settings: set speed 1000, duplex full, and switchport access vlan 1 (or a common trunk native VLAN).

Also ensure both sides use the same LACP mode (both active or active/passive); here SW2's Gi0/2 is passive, which is acceptable with SW1's active, so the primary issue is the mismatched physical and VLAN parameters. After correction, the channel will form.

Exam trap

Do not focus solely on LACP mode mismatches; always check physical parameters (speed, duplex) and VLAN consistency first. Mismatched native VLANs are a common cause of EtherChannel failures.

Why the other options are wrong

The specific factual error is assuming that LACP mode must match on both sides; active/passive is acceptable.

The specific factual error is that the solution should aim for optimal performance, not just consistency; using 100/half is technically possible but not the best practice.

The specific factual error is that trunking does not fix speed/duplex mismatches, and the native VLAN must be consistent.

Practice this question →

PBQhard

You are connected to SW1. Configure an LACP EtherChannel between SW1 and SW2 using interfaces GigabitEthernet0/1 and GigabitEthernet0/2. Set the channel-group mode to active on both switches. Verify that the port-channel interface is configured with VLAN 100 as an access port. Then, troubleshoot and fix the issue that prevents the EtherChannel from forming due to a mismatched speed on one of the member links. After correction, verify the EtherChannel is up with 'show etherchannel summary'.

Hints

•Check the speed and duplex settings on all member interfaces.
•LACP requires identical speed and duplex on all ports in the channel.
•Use the 'speed' and 'duplex' commands under the interface to match the working member.

A.Set speed 1000 and duplex full on interface GigabitEthernet0/2 of SW1, ensuring the corresponding interface on SW2 has matching settings, then verify with 'show etherchannel summary'.

B.Change the channel-group mode to desirable on both switches and verify with 'show etherchannel summary'.

C.Remove the access VLAN configuration from the port-channel interface and configure it as a trunk port instead.

D.Configure the channel-group mode to passive on SW1 and active on SW2, then verify with 'show etherchannel summary'.

AnswerA

solution

! SW1
interface GigabitEthernet0/2
speed 1000
duplex full

Why this answer

The EtherChannel fails because interface GigabitEthernet0/2 on SW1 has a mismatched speed (likely 100 Mbps) compared to the other member link (1000 Mbps). LACP requires all member ports to have identical speed and duplex. The solution is to set the speed on Gi0/2 to 1000 and duplex to full.

After correction, the port will bundle, and the port-channel will come up. Verification with 'show etherchannel summary' should show both ports as 'P' (bundled) and the port-channel as 'SU' (in use, Layer2).

Exam trap

Do not confuse LACP modes (active/passive) with PAgP modes (desirable/auto). Also, remember that physical parameters like speed and duplex must match across all member ports; logical configurations like VLAN or trunking are separate but must also be consistent. Always verify the root cause before changing unrelated settings.

Why the other options are wrong

The specific factual error is that 'desirable' is a PAgP mode, not LACP. LACP uses 'active' and 'passive' modes.

The specific factual error is that the problem is physical (speed mismatch), not logical (VLAN/trunking). Changing the port type does not address the root cause.

The specific factual error is that the speed mismatch is the root cause, not the LACP mode. Even with correct modes, the EtherChannel will not form if speeds differ.

Practice this question →

MCQmedium

A two-switch EtherChannel bundle is configured with LACP. One side uses active mode on both member links, while the other side uses passive mode on both member links. What is the result?

A.The bundle forms successfully

B.The links remain individual because both sides must use active

C.The bundle forms only if PAgP is also enabled

D.The channel comes up but forwards only one VLAN

AnswerA

An LACP EtherChannel bundle forms successfully when at least one side is configured in active mode. In this scenario, the active-mode switch will proactively send LACP PDUs to initiate negotiation. The passive-mode switch, while not initiating, will listen for and respond to these incoming PDUs. This mutual exchange of LACP information satisfies the protocol's requirements for link aggregation, allowing the bundle to establish and operate correctly.

Why this answer

LACP forms a channel when at least one side actively sends negotiation frames. Active-to-passive works. Passive-to-passive would fail, but that is not the case here.

Exam trap

Ensure you know that LACP only needs one side in active mode to form a channel; both sides in passive mode would fail.

Why the other options are wrong

LACP does not require both sides to be in active mode; active/passive is a valid combination. The passive side will respond to LACP packets from the active side, forming the bundle.

PAgP is a Cisco proprietary protocol and is not required for LACP. LACP and PAgP are independent; enabling PAgP does not affect LACP negotiation.

EtherChannel, once formed, forwards all VLANs allowed on the trunk or access ports. There is no mechanism in LACP that restricts the bundle to a single VLAN.

Practice this question →

MCQhard

Two switches are configured for LACP EtherChannel. One side is set to passive and the other side is also set to passive. What is the most likely outcome?

A.The EtherChannel will not form because neither side initiates LACP negotiation.

B.The EtherChannel always forms because passive mode is preferred.

C.The links automatically become a routed interface.

D.The switches delete the bundle configuration automatically.

AnswerA

In LACP, passive mode places the port in a listening state and does not transmit negotiation packets; it only responds to incoming LACP PDUs. Since both switches are configured passive, neither sends an LACP PDU, so the negotiation never begins. Consequently, the EtherChannel remains down and the individual ports stay in their normal operational state as separate access/trunk links.

Why this answer

The EtherChannel will not form because LACP passive mode only listens for negotiation; it does not initiate it. When both sides are set to passive, neither side sends LACP packets, so the bundle cannot be established. This is a deterministic outcome, not merely unlikely.

Exam trap

Ensure at least one side is set to active in LACP configurations to avoid non-formation of the channel.

Why the other options are wrong

Passive mode does not initiate LACP negotiation; it only responds to incoming LACPDUs. Therefore, with both sides passive, no LACPDUs are exchanged, and the EtherChannel will not form. The statement that passive mode is preferred is incorrect; active mode is typically used on at least one side to initiate the channel.

LACP operates at Layer 2 and does not change the interface type. The ports remain switchports (Layer 2) unless explicitly configured with 'no switchport'. LACP mode has no effect on Layer 3 routing functionality.

LACP configuration is not automatically deleted when negotiation fails. The configuration remains in the running-config, and the ports will simply not form an EtherChannel. The administrator must manually remove the configuration if desired.

Practice this question →

MCQhard

An EtherChannel should form using LACP between two switches. One side is configured for LACP active, and the other side is configured for LACP active. What is the expected result if the other link settings also match?

A.The EtherChannel should form if the other interface settings are compatible.

B.The channel fails because both sides must be passive.

C.The channel becomes a routed interface automatically.

D.All VLAN tags are removed from the bundle by default.

AnswerA

A valid LACP EtherChannel can form with both switches in active mode because active interfaces actively transmit LACP protocol data units (PDUs) and negotiate the bundle. As long as the physical interface settings (speed, duplex, allowed VLANs, trunk encapsulation, and switchport mode) are consistent on both sides, the channel will come up. The active/active pairing is a standard and robust configuration for dynamic link aggregation.

Why this answer

The EtherChannel should form successfully if the underlying link settings are compatible. LACP active/active is a valid combination, as both switches actively negotiate the bundle. However, the channel does not automatically become a routed interface (option C is incorrect because EtherChannel can operate as Layer 2 or Layer 3 depending on configuration, not automatically due to LACP mode).

Additionally, VLAN tags are not removed by default from the bundle (option D is incorrect; VLAN tagging is preserved based on the switchport mode and allowed VLAN settings). The key troubleshooting point is to ensure that other interface parameters such as speed, duplex, and VLAN settings match across the member ports.

Exam trap

Don't confuse LACP active/active with incompatible settings; they are designed to negotiate successfully.

Why the other options are wrong

LACP passive/passive is the pairing that fails to form an EtherChannel because both sides wait for the other to initiate negotiation, resulting in no LACP PDUs being sent. Active/active is a valid and functional combination.

LACP operates at Layer 2 and does not change the interface type; the EtherChannel remains a Layer 2 port-channel unless explicitly configured with 'no switchport' or an IP address. The question does not mention any Layer 3 configuration.

EtherChannel formation does not alter VLAN tagging; if the interfaces are trunk ports, VLAN tags remain intact. The bundle simply aggregates bandwidth while preserving existing VLAN configurations.

Practice this question →

MCQhard

Two switches should form an EtherChannel using LACP. One side is configured active and the other passive. If the port settings otherwise match, what is the expected result?

A.The EtherChannel should form if the other interface settings are compatible.

B.The EtherChannel fails because both sides must be active.

C.the bundle forms but only in PAgP mode

D.only the active side attempts to bundle

AnswerA

This is correct because active/passive is a valid LACP negotiation pairing.

Why this answer

The EtherChannel should form successfully. In plain language, active mode initiates LACP negotiation and passive mode listens and responds. Because one side is active, the negotiation can begin and the bundle can come up as long as the underlying interface settings are compatible.

This is a standard LACP pairing. The important lesson is that active/passive works, while passive/passive usually does not. The correct answer is the one that recognizes active/passive as a valid combination.

Exam trap

Remember that active/passive works for LACP, but passive/passive does not initiate negotiation.

Why the other options are wrong

LACP and PAgP are incompatible, so the bundle cannot form in PAgP mode when one side uses LACP.

The passive side will respond to LACP negotiations, so both sides participate and the bundle forms.

Practice this question →

MCQhard

An EtherChannel uses LACP. One side is configured correctly, but the peer side has a different switchport mode on one of the member links. What is the most likely result?

A.The bundle may fail to form correctly because the member-link settings are inconsistent.

B.The switch automatically rewrites the peer configuration to match.

C.LACP converts the mismatched link into a routed interface automatically.

D.The mismatched link is placed in a spanning-tree blocking state.

AnswerA

When LACP is enabled on the local switch but the member links are not configured with identical parameters—such as speed, duplex, VLAN allowed lists, or trunk mode—the negotiation will fail or result in a suspended port-channel. LACP requires the same physical and administrative settings on every member link; otherwise, the misconfigured links will not join the channel group, and the bundle will either stay down or operate intermittently. The result is not a partial bundle but a failure to form the full port-channel as intended.

Why this answer

The most likely result is that the bundle will not form cleanly because EtherChannel requires member links to agree on important operational settings. In practical terms, LACP negotiation alone is not enough. The links also need compatible characteristics such as switchport mode, VLAN handling, speed, and duplex where relevant.

This is a common troubleshooting pattern. It tests whether you know that bundle membership depends on configuration consistency, not just on enabling LACP.

Exam trap

Do not assume LACP can resolve all configuration mismatches. Ensure all settings are consistent across member links.

Why the other options are wrong

Switches do not automatically rewrite peer configurations; configuration changes must be made manually or via network automation tools. LACP only negotiates parameters like speed and duplex, not switchport mode or VLAN settings.

LACP operates at Layer 2 and does not change the interface type; a mismatched link remains a Layer 2 interface. Converting to a routed interface requires manual configuration with 'no switchport' command.

This is incorrect because a switchport mode mismatch in an EtherChannel typically causes the link to be suspended or placed into an errdisable state, not into a spanning-tree blocking state. Spanning tree deals with loops, not port-channel parameter mismatches.

Practice this question →

MCQhard

A network engineer configures an EtherChannel between two switches. Switch A's interface is set with channel-group 1 mode active, while Switch B's identical interface is set with channel-group 1 mode auto. When verifying with show etherchannel summary, the engineer observes that the port-channel interface is down and the physical interfaces are not bundled. What is the most likely cause of the problem?

A.The LACP system priority on the active side must be lower than the auto side.

B.The mode 'auto' is a PAgP negotiation mode that is incompatible with the LACP active mode.

C.LACP requires one side to be active and the other passive; two active interfaces will not bundle.

D.The physical interfaces must be shut down and then re-enabled after configuring LACP for the bundle to form.

AnswerB

The mode 'auto' is one of the two PAgP negotiation modes (the other being 'desirable'), whereas LACP uses 'active' and 'passive'. PAgP and LACP are entirely separate protocols with different frame formats and state machines, so an interface set to 'auto' cannot form an EtherChannel with an interface set to 'active'. To create a bundle with LACP, both sides must use LACP modes, such as active/active or active/passive, not PAgP modes.

Why this answer

'active' is an LACP mode that initiates negotiations, while 'auto' is a PAgP mode that passively waits for PAgP packets. Since LACP and PAgP are incompatible protocols, the interfaces will never negotiate a bundle, leaving the port-channel down. The engineer must use matching protocol modes (e.g., both LACP active/passive or both PAgP desirable/auto) for EtherChannel to form.

Exam trap

Cisco often tests the confusion between LACP and PAgP mode keywords, especially the similarity between 'active' (LACP) and 'auto' (PAgP), leading candidates to assume they are compatible or to focus on priority or interface state rather than protocol mismatch.

Why the other options are wrong

LACP priority is not required for basic negotiation and does not cause a failure to bundle.

Active/active LACP successfully negotiates, so this is not the cause.

Bouncing interfaces is not required to trigger LACP negotiation.

Practice this question →

PBQhard

You are connected to SW1 via console. SW1 is a Layer 2 switch connected to SW2 via three links (G0/1, G0/2, G0/3) that should form an EtherChannel using LACP. Currently, the interfaces are configured as access ports in VLAN 1. Configure the three interfaces as a LACP EtherChannel trunk that carries VLANs 1-100, and ensure the port-channel interface is operational.

Network Topology

Hints

•Create the port-channel interface first, then assign physical ports with 'channel-group'.
•Use 'mode active' for LACP.

A.interface port-channel 1 switchport mode trunk switchport trunk allowed vlan 1-100 interface range g0/1-3 channel-group 1 mode active switchport mode trunk

B.interface port-channel 1 switchport mode trunk switchport trunk allowed vlan 1-100 interface range g0/1-3 channel-group 1 mode passive switchport mode trunk

C.interface port-channel 1 switchport mode access switchport access vlan 1 interface range g0/1-3 channel-group 1 mode active switchport mode trunk

D.interface port-channel 1 switchport mode trunk switchport trunk allowed vlan 1-100 interface range g0/1-3 channel-group 1 mode on switchport mode trunk

AnswerA

solution

! SW1
interface port-channel 1
switchport mode trunk
switchport trunk allowed vlan 1-100
interface gigabitethernet0/1
channel-group 1 mode active
interface gigabitethernet0/2
channel-group 1 mode active
interface gigabitethernet0/3
channel-group 1 mode active

Why this answer

The port-channel interface is created and configured as a trunk with allowed VLANs. Physical interfaces are assigned to the channel-group with LACP active mode, which negotiates the EtherChannel with the peer. The trunk is then operational for VLANs 1-100.

Exam trap

Remember that LACP requires at least one side to be in active mode to initiate negotiation. Also, the port-channel interface configuration must match the physical interfaces' switchport mode. Do not confuse 'mode on' (static) with LACP modes.

Why the other options are wrong

The specific factual error: LACP passive mode does not initiate negotiation; it only responds. For the EtherChannel to form, at least one side must be active.

The specific factual error: The port-channel interface and physical interfaces must have consistent switchport mode configuration. Here, the port-channel is access while physical are trunk, causing a mismatch.

The specific factual error: 'channel-group mode on' creates a static EtherChannel without LACP. The question requires LACP, so this does not meet the requirement.

PBQhard

You are connected to SW1. A LACP EtherChannel between SW1 and SW2 has already been configured using interfaces GigabitEthernet0/1 and GigabitEthernet0/2 with channel-group 1 mode active on both sides and assigned to VLAN 100. However, the channel is not forming because of a speed/duplex mismatch. The correct interface settings for this network are speed 1000 and duplex full. Interface GigabitEthernet0/1 is already configured with these settings. Only interface GigabitEthernet0/2 needs to be corrected. Identify the configuration change needed to resolve the mismatch and verify the EtherChannel is up with 'show etherchannel summary'.

Network Topology

Hints

•Check the speed and duplex settings on both member interfaces.
•LACP requires all ports in the channel to have identical configuration.
•Use the 'show interfaces status' command to quickly see speed/duplex mismatches.

A.Configure interface GigabitEthernet0/2 with 'speed 1000' and 'duplex full', then verify the EtherChannel is up.

B.Configure interface GigabitEthernet0/1 with 'speed 100' and 'duplex half', then verify the EtherChannel is up.

C.Configure interface GigabitEthernet0/2 with 'speed auto' and 'duplex auto', then verify the EtherChannel is up.

D.Configure interface GigabitEthernet0/2 with 'channel-group 1 mode active' and 'switchport access vlan 100', then verify the EtherChannel is up.

AnswerA

solution

! SW1
interface GigabitEthernet0/2
speed 1000
duplex full
end
show etherchannel summary

Why this answer

The EtherChannel is not forming because GigabitEthernet0/2 is configured with speed 100 and duplex half, while GigabitEthernet0/1 is speed 1000 and duplex full. LACP requires all member ports to have identical speed and duplex settings. To fix this, configure GigabitEthernet0/2 with speed 1000 and duplex full, matching GigabitEthernet0/1.

After correction, the ports should bundle in Port-channel1 and show as bundled (P) in 'show etherchannel summary'.

Exam trap

The trap is that candidates may overlook the speed/duplex mismatch and focus only on the LACP mode or VLAN configuration. Always verify that all physical parameters match before troubleshooting EtherChannel formation.

Why the other options are wrong

The specific factual error is that the question implies the correct configuration should use speed 1000 and duplex full, not downgrade to 100/half. Also, LACP requires identical settings, but the goal is to match the higher speed.

The specific factual error is that auto-negotiation does not guarantee matching settings when one side is manually configured. The mismatch would persist.

The specific factual error is that the question explicitly states a speed/duplex mismatch prevents the channel from forming, and this option does not correct that mismatch.

Practice this question →

PBQhard

You are connected to SW1. Two switches, SW1 and SW2, are connected via four GigabitEthernet links. Configure LACP EtherChannel between them using interfaces GigabitEthernet0/1 through GigabitEthernet0/4 on SW1. Set the channel-group mode to active on SW1. The port-channel interface must be configured as a trunk, allowing VLANs 10, 20, 30. However, the EtherChannel is not forming. The current configuration is shown below. Identify and fix the issue, then verify the EtherChannel is operational.

Network Topology

Hints

•Compare the Layer 2/Layer 3 status of the port-channel interface with the member interfaces.
•Check the 'show etherchannel summary' flags: 'SD' means Layer 3 and down; 'SU' means Layer 2 and up.
•The port-channel interface must match the operational mode (Layer 2) of the member switchports.

A.Remove 'no switchport' and IP address from Port-channel1, then configure 'switchport mode trunk' and 'switchport trunk allowed vlan 10,20,30'.

B.Change the channel-group mode on the member interfaces from active to passive.

C.Add the 'switchport nonegotiate' command to the member interfaces.

D.Configure the member interfaces with 'channel-group 1 mode on' instead of active.

AnswerA

solution

! SW1
interface Port-channel1
no ip address 192.168.1.1 255.255.255.0
no no switchport
switchport mode trunk
switchport trunk allowed vlan 10,20,30

Why this answer

The EtherChannel is not forming because the Port-channel1 interface is configured as a Layer 3 interface (no switchport, IP address), while the member interfaces are Layer 2 switchports (switchport mode trunk). This mismatch prevents the channel from bundling. To fix this, configure Port-channel1 as a Layer 2 trunk interface with the same allowed VLANs.

The solution: remove the no switchport command and the IP address, then apply switchport mode trunk and switchport trunk allowed vlan 10,20,30. After correction, the ports should bundle and the show etherchannel summary will show the ports as bundled (P) and the port-channel as Layer 2 (S).

Exam trap

The exam trap is that candidates often focus on LACP modes or trunk negotiation but overlook the Layer 2/Layer 3 mismatch between the port-channel interface and member interfaces. Always ensure the port-channel interface is configured as either Layer 2 or Layer 3 to match the member ports.

Why the other options are wrong

The specific factual error: The problem is a Layer 2/Layer 3 mismatch, not the LACP mode. Active mode is valid and commonly used.

The specific factual error: 'switchport nonegotiate' affects trunk negotiation, not EtherChannel bundling.

The specific factual error: The mode change does not fix the interface type mismatch; the port-channel must be Layer 2 to match the member ports.

Practice this question →

MCQhard

Two switches should form an EtherChannel with LACP. One side is set to active and the other is set to passive. If the remaining interface settings match, what is the expected result?

A.The EtherChannel should form successfully.

B.The EtherChannel fails because both sides must be active.

C.The interfaces automatically become routed ports.

D.The switches delete the port-channel automatically.

AnswerA

In LACP, an interface configured as active actively sends LACP PDUs, while passive only responds to incoming PDUs. When one switch is active and the other passive, the active side's PDUs trigger the passive side to reply, allowing both devices to exchange port attributes and form a stable EtherChannel. The active/passive configuration is explicitly supported by the IEEE 802.3ad standard and is a common deployment for connecting to switches that do not support the active mode.

Why this answer

The EtherChannel should form successfully. In practical terms, active mode initiates LACP negotiation and passive mode listens and responds. Because one side is actively starting the negotiation, the bundle can come up if the interfaces also match in operational settings such as speed, duplex, switchport mode, and VLAN characteristics.

This is a classic LACP pairing question. Active/passive works. Passive/passive is the combination that usually fails to start the bundle.

Exam trap

Remember, LACP requires only one side to be active; passive mode will still respond.

Why the other options are wrong

LACP allows an active port to form a bundle with a passive port; the passive side simply waits for LACP packets from the active side. Therefore, both sides do not need to be active.

LACP mode does not change the Layer 2 or Layer 3 status of interfaces; it only controls the negotiation of EtherChannel bundling. Interfaces remain as switchports unless explicitly configured as routed ports.

LACP negotiation failure does not automatically delete the port-channel interface or its configuration. The port-channel remains, but the member ports will not bundle and will operate as individual ports.

Practice this question →

Drag & Dropmedium

Drag and drop the following steps into the correct order to configure an LACP EtherChannel on Cisco IOS-XE switches.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

Why this order

First, enter global config mode. Then create the port-channel interface. Next, configure the channel-group mode on each physical interface to active for LACP.

Finally, verify the configuration.

Exam trap

A common trap is to configure the channel-group mode on physical interfaces before creating the port-channel interface, or to forget that global configuration mode is the first step. Always remember the sequence: global config -> port-channel interface -> physical interface channel-group -> verification.

Practice this question →

Multi-Selectmedium

Which TWO statements correctly describe the configuration and verification of EtherChannel with LACP?

Select 2 answers

A.LACP uses the 'active' and 'passive' modes to negotiate an EtherChannel.

B.The 'show etherchannel summary' command displays the channel group number, port-channel interface, member ports, and their status.

C.LACP uses the 'auto' and 'desirable' modes to negotiate an EtherChannel.

D.The 'show etherchannel summary' command shows the LACP system priority for each channel.

E.An EtherChannel can be formed only if all member ports use the same LACP mode.

AnswersA, B

This statement is correct. LACP negotiation relies on two modes: 'active' and 'passive'. An interface in 'active' mode actively sends LACP packets to initiate the link aggregation, while one in 'passive' mode waits for a response and only sends packets after receiving them. For an EtherChannel to form, at least one side must be 'active'; if both sides are 'passive', the channel will not come up because no negotiation is initiated.

Why this answer

LACP (IEEE 802.3ad) uses 'active' and 'passive' modes to negotiate an EtherChannel. Option B is correct because the 'show etherchannel summary' command displays the channel group number, port-channel interface, member ports, and their status flags (e.g., P for in port-channel, S for suspended). Option C is incorrect because 'auto' and 'desirable' are PAgP modes, not LACP modes.

Option D is incorrect because 'show etherchannel summary' does not show LACP system priority; that is displayed with 'show lacp sys-id' or 'show etherchannel detail'. Option E is incorrect because an EtherChannel can be formed with mismatched LACP modes as long as at least one side is 'active'; for example, 'active' + 'passive' works.

Exam trap

Cisco often tests the distinction between LACP modes ('active'/'passive') and PAgP modes ('auto'/'desirable'), and candidates frequently confuse which protocol uses which set of modes.

Why the other options are wrong

LACP does not use 'auto' and 'desirable' modes; those are PAgP modes.

The 'show etherchannel summary' command does not display LACP system priority; that is shown via 'show lacp sys-id' or 'show etherchannel detail'.

An EtherChannel can be formed even if member ports use different LACP modes (e.g., active and passive), as long as at least one side is active.

Practice this question →

MCQmedium

A network engineer checks EtherChannel status on a switch and sees the following output: Group Port-channel Protocol Ports ------+-------------+---------+----------------------------- 1 Po1(SD) LACP Gi1/0/1(s) Gi1/0/2(I) What is the most likely reason the EtherChannel is not forwarding traffic?

A.The member interfaces have mismatched speed or duplex settings

B.The port channel is Layer 3 instead of Layer 2

C.At least one member interface is not bundled correctly, so the logical channel is down

D.LACP requires exactly four links to form a bundle

AnswerC

Correct. This is correct. The logical EtherChannel is down because the physical members are not properly bundled. The status display is telling you that the switch did not build a working aggregated link, so the port-channel cannot carry traffic as intended.

Why this answer

The safest conclusion from this output is that the member interfaces are not successfully participating in the bundle, so the logical port-channel is down. Cisco exam questions often test whether you can read the status flags without overcommitting to a very specific root cause that the exhibit does not explicitly prove. One member is suspended and another is not bundled into the channel correctly, so the EtherChannel never reaches a healthy forwarding state.

In the real world, that can happen because of trunk mismatches, allowed VLAN mismatches, native VLAN problems, inconsistent channel-group settings, or negotiation issues. The key exam skill is recognizing that the bundle itself failed, not guessing one hidden configuration line that is not shown.

Exam trap

Avoid assuming the problem is due to physical layer issues like speed or duplex when the output suggests a configuration mismatch.

Why the other options are wrong

The output shows individual port statuses (s) and (I), which indicate LACP negotiation states, not speed/duplex mismatches. While speed/duplex mismatches can cause EtherChannel issues, the specific flags in the exhibit point to a bundling problem, not a mismatch.

A Layer 3 port-channel can function correctly if configured properly. The output does not indicate any Layer 2 vs Layer 3 mismatch; the problem is that the member interfaces are not successfully bundling into the logical channel, as shown by the (s) and (I) status flags.

LACP does not require exactly four links; it can form bundles with 2 to 8 active links (and up to 16 total with standby). The exhibit shows only two member ports, which is perfectly valid for an EtherChannel.

Practice this question →

PBQhard

You are connected to SW1 via the console. SW1 is a Layer 2 switch with two links to SW2 configured as an EtherChannel using LACP. The EtherChannel is not coming up. Interface G0/2 was accidentally configured as an access port in VLAN 10, while G0/1 is configured as a trunk. The administrator wants to use LACP to bundle the links. Troubleshoot and fix the configuration to bring up the EtherChannel.

Hints

•All interfaces in an EtherChannel must have identical configuration.
•Check if the interfaces are in the same VLAN or trunk mode.
•LACP active mode requires matching configurations on both ends.

A.Change interface G0/2 to trunk mode and ensure both interfaces have the same allowed VLAN list.

B.Change interface G0/1 to access VLAN 10 to match G0/2.

C.Remove the access VLAN configuration from G0/2 and leave it as a default switchport (dynamic desirable).

D.Change the EtherChannel mode from LACP to PAgP on both switches.

AnswerA

solution

! SW1
interface GigabitEthernet0/2
no switchport access vlan 10
switchport mode trunk

Why this answer

The EtherChannel was down because interface G0/2 was an access port in VLAN 10, while G0/1 was a trunk. For LACP to bundle the links, all member interfaces must have the same configuration, including VLAN and trunk settings. Changing G0/2 to trunk mode resolved the issue.

Exam trap

Do not confuse the requirement for consistent interface configurations with the negotiation protocol. The most common cause of EtherChannel failure is mismatched VLAN or trunk settings, not the protocol (LACP vs PAgP). Always verify that all member ports have identical configurations.

Why the other options are wrong

The specific factual error is that changing G0/1 to access VLAN 10 would not resolve the mismatch if the intended configuration is trunking. It would only create a different mismatch if the other side expects trunking.

The specific factual error is that dynamic desirable mode does not ensure trunking; it relies on DTP negotiation, which may fail if the other side is set to trunk. Additionally, the VLAN mismatch (access vs trunk) would still prevent EtherChannel formation.

The specific factual error is that the protocol does not affect the requirement for consistent interface configurations. Both LACP and PAgP require identical VLAN and trunk settings on all member ports.

MCQmedium

Two switches are connected with EtherChannel using LACP. One side is configured with mode active and the other side with mode passive. What happens?

A.The channel forms successfully

B.The channel stays down because both sides must be active

C.The channel forms only if PAgP is also enabled

D.The channel becomes a static Port-Channel

AnswerA

LACP's active/passive mode is a standard, valid combination. The active switch actively sends LACP PDUs (protocol data units) to negotiate the link, while the passive switch listens and responds, allowing the port-channel to form. Since one side is active, the negotiation completes and the EtherChannel becomes operational as a dynamic LACP bundle.

Why this answer

LACP forms an EtherChannel when at least one side actively negotiates. Active plus passive is a valid combination, so the bundle comes up if the physical settings match.

Exam trap

A frequent exam trap is believing that both sides of an LACP EtherChannel must be configured in active mode for the channel to form. This misconception leads to the incorrect assumption that active-passive combinations will fail. In reality, LACP requires only one side to be active to initiate negotiation, while the other side can be passive and respond.

Another trap is confusing LACP with PAgP, expecting that enabling PAgP alongside LACP will help form the channel, which is false because these protocols are incompatible. Understanding these nuances prevents misinterpretation of EtherChannel negotiation behavior on the exam.

Why the other options are wrong

This option is incorrect because both sides do not need to be active. One side active and the other passive is sufficient for LACP negotiation and channel formation.

This option is incorrect because PAgP is a different, Cisco proprietary protocol and does not work alongside LACP. Enabling PAgP does not affect LACP negotiation.

This option is incorrect because configuring one side as active and the other as passive uses LACP negotiation, not a static Port-Channel. Static Port-Channels require manual configuration on both ends without negotiation.

Practice this question →

MCQhard

Two switches are connected using four Gigabit Ethernet interfaces configured as an EtherChannel with LACP. The network administrator notices that only two of the four interfaces are active in the port-channel, and the other two are in a suspended state. Upon further investigation, the administrator finds that the two inactive interfaces correspond to remote interfaces that are configured with the 'on' mode, while the active ones correspond to remote interfaces configured with LACP active/passive. The administrator also verifies that all local interfaces have the same speed, duplex, and VLAN. What is the most likely cause of the suspended interfaces?

A.The interfaces are in err-disabled state due to a spanning-tree loop.

B.The remote switch interfaces corresponding to the suspended local interfaces are configured with the 'on' mode instead of 'active' or 'passive' for LACP.

C.The port-channel interface is shutdown.

D.There is a mismatch in the allowed VLANs on the member interfaces.

AnswerB

When one switch has LACP active/passive and the other has 'on' (static), LACP negotiation fails, and the ports become suspended. Changing the remote switch to 'active' or 'passive' allows LACP to negotiate and bundle the ports.

Why this answer

LACP requires both ends of a link to be configured in either 'active' or 'passive' mode to negotiate an EtherChannel. If some remote interfaces are set to 'on' mode (static EtherChannel), LACP negotiation fails on those links, causing the corresponding local LACP-enabled interfaces to remain in a suspended state. The local switch detects that LACP PDUs are not received on those interfaces and suspends them to prevent misconfiguration.

The other two interfaces with correctly configured remote peers form the EtherChannel successfully.

Exam trap

Cisco often tests the misconception that all interfaces must match in speed, duplex, and VLAN to form an EtherChannel, but the trap here is that the LACP mode mismatch (active/passive vs. on) is the specific cause of suspended interfaces even when other parameters are consistent.

Why the other options are wrong

The exhibit shows the ports as suspended, not err-disabled. Spanning-tree loops typically cause err-disable, not suspension.

The port-channel is up (U), so it is not shutdown.

The scenario explicitly states that all interfaces are configured with the same VLAN, so this is not the cause.

Practice this question →

PBQhard

You are connected to Switch1. Configure an LACP EtherChannel between Switch1 and Switch2 using interfaces GigabitEthernet0/1 and GigabitEthernet0/2. The channel must be in active mode on both sides, and the port-channel interface must have VLAN 10 as the access VLAN. The current configuration has a speed/duplex mismatch and inconsistent VLAN assignments preventing the channel from forming. Verify the channel is up using 'show etherchannel summary'.

Network Topology

Hints

•Check that all member interfaces have the same speed and duplex settings.
•Ensure all interfaces (including the port-channel) are in the same VLAN.
•Both sides must use LACP active mode for the channel to form.

A.Set speed auto on Gi0/1 and Gi0/2, set duplex auto on both, change access VLAN on Gi0/2 to 10, change access VLAN on Port-channel1 to 10, and set channel-group mode active on both interfaces.

B.Set speed 1000 on Gi0/1, set duplex full on Gi0/1, change access VLAN on Gi0/1 to 20, change access VLAN on Port-channel1 to 20, and set channel-group mode passive on both interfaces.

C.Set speed 100 on Gi0/2, set duplex half on Gi0/2, change access VLAN on Gi0/1 to 20, change access VLAN on Port-channel1 to 20, and set channel-group mode desirable on both interfaces.

D.Set speed auto on Gi0/1 and Gi0/2, set duplex auto on both, change access VLAN on Gi0/1 to 10, change access VLAN on Port-channel1 to 10, and set channel-group mode active on Gi0/1 and passive on Gi0/2.

AnswerA

solution

! Switch1
interface gigabitethernet0/1
speed auto
duplex auto
channel-group 1 mode active
exit
interface gigabitethernet0/2
speed auto
duplex auto
switchport access vlan 10
channel-group 1 mode active
exit
interface port-channel 1
switchport access vlan 10
end

Why this answer

The EtherChannel is not forming due to three issues: (1) Speed mismatch: Gi0/1 is set to 100 Mbps while Gi0/2 is 1000 Mbps; both must match (e.g., auto). (2) Duplex mismatch: Gi0/1 is half-duplex, Gi0/2 is full-duplex; both must be the same (e.g., full). (3) VLAN mismatch: Gi0/1 is in VLAN 10, Gi0/2 in VLAN 20, and Port-channel1 is in VLAN 1; all access VLANs must be consistent (set to VLAN 10). Additionally, the channel-group mode should be 'active' on both interfaces for LACP. The solution involves setting speed and duplex to auto, changing the access VLAN on Gi0/2 and the port-channel to VLAN 10, and setting channel-group mode to active.

Exam trap

The exam trap here is that candidates may focus only on resolving the speed/duplex and VLAN mismatches but forget to check the LACP mode requirement. Also, they might confuse LACP modes (active/passive) with PAgP modes (desirable/auto). Always verify that the mode matches the protocol and the requirement.

Why the other options are wrong

The specific factual error: passive mode on both sides will not form an LACP EtherChannel because neither side initiates negotiation; at least one side must be active.

The specific factual error: 'desirable' is a PAgP mode; LACP uses 'active' or 'passive'. Using 'desirable' would not form an LACP EtherChannel.

The specific factual error: the requirement explicitly states 'active mode on both sides', so setting one side to passive violates the requirement, even though the channel might still form.

Practice this question →

MCQhard

An EtherChannel between two switches is configured for LACP. One switch shows the member interfaces as bundled, while the other shows them as individual interfaces. Which explanation is most likely if both sides are using LACP?

A.The member interface settings do not match closely enough for bundling, even though both sides use LACP.

B.LACP always requires one side to use PAgP as a backup.

C.EtherChannel cannot operate on switch trunks.

D.One switch must disable STP before EtherChannel can form.

AnswerA

LACP negotiation alone does not guarantee bundling; the member interfaces must also share identical physical and logical parameters such as speed, duplex, VLAN membership, native VLAN, and trunk mode. If any of these settings differ, the LACP control plane will detect the mismatch and keep the ports in a standalone state. Thus, even with LACP active on both ends, inconsistent interface configurations prevent the EtherChannel from forming.

Why this answer

The most likely explanation is that some other interface settings do not match, even though both sides are using the same EtherChannel protocol. In practical terms, LACP alone is not enough. The candidate member interfaces also need to agree on characteristics such as speed, duplex, switchport mode, allowed VLANs where relevant, and other channel-related settings. If they do not, one side may treat the links as separate instead of bundling them.

This is a common troubleshooting pattern because it tests whether you know that EtherChannel success depends on more than just the negotiation protocol name.

Exam trap

Don't assume LACP alone ensures bundling; check all interface settings for consistency.

Why the other options are wrong

This option is incorrect because LACP (Link Aggregation Control Protocol) does not require PAgP (Port Aggregation Protocol) as a backup; they are separate protocols. LACP can operate independently without needing PAgP on either side of the EtherChannel.

This option is incorrect because EtherChannel can indeed operate on switch trunks, allowing multiple VLANs to be carried over a single logical link. The issue in the question pertains to LACP configuration mismatches, not trunking capabilities.

This option is incorrect because Spanning Tree Protocol (STP) does not need to be disabled for EtherChannel to form; EtherChannel can operate alongside STP. Disabling STP can lead to network loops and is not a requirement for EtherChannel functionality.

Practice this question →

MCQhard

Exhibit: SW1 is configured for EtherChannel with LACP, but the bundle does not form. What is the most likely cause?

A.The interfaces should use PAgP instead of LACP on both ends

B.One side is using LACP and the other side is using a static EtherChannel mode

C.The links must be routed ports before EtherChannel can form

D.EtherChannel requires three or more member links

AnswerB

The correct explanation is that EtherChannel will not form because the interface configurations are incompatible: one side is running LACP in active mode, which sends LACP PDUs to negotiate a channel, while the other side is configured with a static mode (mode on), which does not send or process LACP PDUs. Without LACP negotiation from both peers, the switch sees no valid LACP partner and refuses to bundle the links. To fix this, both ends must use LACP (active/passive) or both must use static mode.

Why this answer

For an LACP EtherChannel to form, both sides must negotiate with LACP using active or passive mode. One side here is set to channel-group mode on, which creates a static channel and does not speak LACP. That mismatch prevents the bundle from forming.

Exam trap

Ensure both sides of the EtherChannel are set to negotiate with LACP; avoid static channel settings.

Why the other options are wrong

This option is incorrect because the question specifies that LACP is being used, which is incompatible with PAgP. EtherChannel can operate with either LACP or PAgP, but not both simultaneously.

This option is wrong because EtherChannel can form with access ports or trunk ports, and there is no requirement for the interfaces to be routed ports for EtherChannel to function.

EtherChannel can function with as few as two member links; therefore, requiring three or more member links is not a valid reason for the bundle not forming in this scenario.

Practice this question →

Drag & Dropmedium

Drag and drop the following steps into the correct order to configure an LACP EtherChannel on two Cisco switches using active mode.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

Why this order

To configure an LACP EtherChannel in active mode, you must first enter interface configuration mode on the physical interfaces (e.g., using interface range). Next, assign those interfaces to a channel group using the channel-group command with the mode active keyword; this enables LACP negotiation and ensures the switch actively attempts to form a bundle. After the member ports are configured, you can optionally set parameters on the Port-Channel interface (such as switchport mode trunk).

Finally, verify the EtherChannel is operational with show etherchannel summary. Using mode passive, on, or desirable would not enable LACP active negotiation or would use a different protocol (PAgP), which does not meet the requirement.

Exam trap

Remember that LACP uses active and passive modes, while PAgP uses desirable and auto. Do not confuse the protocols or their modes.

Practice this question →

PBQhard

You are connected to Multilayer Switch SW1. Configure LACP EtherChannel between SW1 and SW2 using ports GigabitEthernet0/1 and GigabitEthernet0/2. Ensure the channel is formed and active. The current configuration has mismatched VLAN assignments and speed/duplex settings preventing the channel from coming up. Verify the channel state using 'show etherchannel summary'.

Network Topology

Hints

•Check that both physical ports have identical speed and duplex settings.
•Ensure the allowed VLAN list on each member port matches the Port-channel interface.
•Use 'show etherchannel summary' to see if ports are in a suspended (D) or bundled (P) state.

A.Configure both Gi0/1 and Gi0/2 with speed 1000, duplex full, and switchport trunk allowed vlan 10,20,30.

B.Configure both Gi0/1 and Gi0/2 with speed 100, duplex half, and switchport trunk allowed vlan 30.

C.Configure both Gi0/1 and Gi0/2 with speed 1000, duplex full, and switchport trunk allowed vlan 10,20.

D.Configure both Gi0/1 and Gi0/2 with speed 1000, duplex full, and switchport mode access.

AnswerA

solution

! SW1
interface GigabitEthernet0/1
switchport trunk allowed vlan 10,20,30
exit
interface GigabitEthernet0/2
speed 1000
duplex full
switchport trunk allowed vlan 10,20,30
exit

Why this answer

The EtherChannel is down because the two member ports on SW1 have inconsistent configurations. GigabitEthernet0/1 is set to speed 1000 and duplex full with allowed VLANs 10,20, while GigabitEthernet0/2 is set to speed 100 and duplex half with allowed VLAN 30. LACP requires all member ports to have identical speed, duplex, and VLAN allowed lists.

To fix, on SW1 configure both Gi0/1 and Gi0/2 with the same speed (1000), duplex (full), and trunk allowed VLANs (10,20,30). The Port-channel interface already has the correct allowed VLANs. After correction, 'show etherchannel summary' should show both ports as bundled (P).

Exam trap

The exam trap is that candidates often focus only on speed/duplex mismatches and forget that VLAN allowed lists must also match. Additionally, they may assume that the Port-channel interface inherits settings from member ports, but in fact, the member ports must match the Port-channel configuration.

Why the other options are wrong

The specific factual error is that LACP requires all member ports to have identical configurations, and this option does not align with the existing Port-channel configuration.

The specific factual error is that the VLAN allowed list must match across all member ports and the Port-channel interface; omitting VLAN 30 will cause inconsistency.

The specific factual error is that LACP requires consistent switchport mode (access or trunk) across all member ports and the Port-channel interface.

Practice this question →

Multi-Selecthard

Which two conditions must match on two switch ports before they can successfully form a Layer 2 EtherChannel? (Choose two.)

Select 2 answers

A.The switchport mode and VLAN settings

B.The STP root bridge ID on both switches

C.The speed and duplex settings

D.The interface description

E.The ARP timeout value

AnswersA, C

For an EtherChannel to operate correctly, each member port on both switches must be assigned the same switchport mode (access or trunk) and, if trunking, the identical set of allowed VLANs. When mode or VLAN permissions differ across links, frames may be dropped or forwarded inconsistently because the channel treats all member ports as a single logical link, and STP or negotiation protocols will reject the bundle if these attributes disagree.

Why this answer

Layer 2 EtherChannel members must have compatible Layer 2 configuration. Port mode, VLAN-related settings, speed, and duplex all need to align for the bundle to form correctly.

Exam trap

Remember that EtherChannel requires consistent speed and duplex settings, and also consistent switchport mode (access or trunk) and allowed VLANs.

Why the other options are wrong

This option is wrong because the STP root bridge ID does not directly affect the formation of an EtherChannel; EtherChannel requires matching port configurations, not spanning tree parameters.

The interface description does not affect the formation of an EtherChannel, as it is merely a label for identification purposes and does not influence Layer 2 connectivity or protocol negotiation.

The ARP timeout value does not affect the formation of a Layer 2 EtherChannel, as EtherChannel operates at Layer 2 and is concerned with port configurations, not Layer 3 settings like ARP.

Practice this question →

MCQhard

Which command output would be the best next step to verify whether the port-channel is operational after configuration changes?

A.show etherchannel summary

B.show ip ospf neighbor

C.show ip route

D.show access-lists

AnswerA

This command displays the EtherChannel bundle status, including the port-channel interface, member ports, and their state (e.g., LACP, PAgP, or static). It directly shows whether the port channel is up and which physical interfaces are bundled, making it the best next step to confirm EtherChannel operation.

Why this answer

The best next step is to check EtherChannel status directly. In practical terms, after fixing the member-link configuration, the quickest verification is to inspect the summary output that shows whether the bundle exists and whether the member ports are actively participating. That is more direct than checking unrelated switching or routing tables.

This is a simulation-style 'what do you verify next' question, which is important for realistic CCNA prep.

Exam trap

Avoid confusing general interface or trunk status with specific EtherChannel status. Always use the command that directly addresses the feature in question.

Why the other options are wrong

The command 'show ip ospf neighbor' is used to display OSPF neighbor relationships, which is not directly related to verifying the operational status of a port-channel. This command would not provide information about the port-channel configuration or status.

The command 'show ip route' is used to display the routing table of a device, which does not provide information about the operational status of a port-channel after configuration changes.

The command 'show access-lists' is not relevant for verifying the operational status of a port-channel; it focuses on access control lists rather than link aggregation status.

Practice this question →

PBQhard

You are connected to SW1. Configure an LACP EtherChannel between SW1 and SW2 using ports GigabitEthernet0/1 and GigabitEthernet0/2. Set the channel-group mode to active on both sides. The port-channel interface should be configured as a trunk allowing VLANs 10, 20, and 30. Initially, the EtherChannel fails to form due to mismatched speed/duplex on one link. Identify and correct the issue, then verify the channel is up and operational.

Network Topology

Hints

•Check the speed and duplex settings on each member interface.
•LACP requires all ports in the channel to have identical speed and duplex.
•Use 'show interfaces status' to quickly see speed/duplex mismatches.

A.Change speed and duplex on Gi0/2 to 1000 and full, then verify with 'show etherchannel summary'.

B.Change the channel-group mode on Gi0/2 to passive, then verify with 'show etherchannel summary'.

C.Change the allowed VLANs on the port-channel to include only VLAN 1, then verify with 'show etherchannel summary'.

D.Change the port-channel interface to access mode, then verify with 'show etherchannel summary'.

AnswerA

solution

! SW1
interface GigabitEthernet0/2
speed 1000
duplex full

Why this answer

The EtherChannel fails because GigabitEthernet0/2 has speed 100 and duplex half, while GigabitEthernet0/1 has speed 1000 and duplex full. LACP requires all member ports to have identical speed and duplex settings. To resolve, change the speed and duplex on Gi0/2 to match Gi0/1: 'speed 1000' and 'duplex full'.

After correction, the channel will bundle. Verify with 'show etherchannel summary' to see both ports in the 'P' (bundled) state.

Exam trap

Do not confuse Layer 1 issues (speed/duplex) with Layer 2 configuration (VLANs, trunking) or LACP mode settings. Always check physical parameters first when an EtherChannel fails to form.

Why the other options are wrong

The specific factual error is that LACP modes must be compatible (active-active or active-passive), but the question states both sides are active, so mode is not the issue.

The specific factual error is that VLAN settings are irrelevant to the physical bundling of ports in an EtherChannel.

The specific factual error is that interface mode is a Layer 2 property unrelated to the physical bundling process.

Practice this question →

MCQhard

A network administrator is configuring a Layer 2 EtherChannel between two switches. Switch A uses 'channel-group 1 mode active', and Switch B uses 'channel-group 1 mode desirable'. All member interfaces are trunk ports with identical allowed VLANs. The EtherChannel fails to form. What is the most likely cause?

A.The switches are using different EtherChannel negotiation protocols.

B.A Layer 2 EtherChannel cannot carry trunk links.

C.The channel-group number must be different on each switch.

D.The member interfaces must be in access mode before the bundle can form.

AnswerA

Switch A is configured for Link Aggregation Control Protocol (LACP) using `mode active`, whereas Switch B is configured for Port Aggregation Protocol (PAgP) using `mode desirable`. LACP and PAgP are distinct EtherChannel negotiation protocols. For an EtherChannel to establish using a negotiation protocol, both connected switches must utilise the identical protocol, as they are incompatible with each other. This protocol mismatch directly causes the EtherChannel to fail.

Why this answer

The two switches are using different negotiation protocols: LACP (active) on one side and PAgP (desirable) on the other. EtherChannel requires both sides to use the same protocol, so this protocol mismatch prevents the bundle from forming. The other settings—trunking, VLAN configuration, and channel-group number—are correctly configured and do not cause the failure.

Exam trap

Ensure both sides of an EtherChannel use the same negotiation protocol; mismatches are a common setup error.

Why the other options are wrong

This option is incorrect because a Layer 2 EtherChannel can indeed carry trunk links, allowing multiple VLANs to be transmitted over the same logical link. The issue with the EtherChannel not forming is more likely related to mismatched negotiation protocols or other configuration errors.

This option is wrong because the channel-group number must be the same on both switches for an EtherChannel to form. Different numbers would prevent the aggregation of the links.

This option is wrong because a Layer 2 EtherChannel can indeed carry trunk links, allowing multiple VLANs to be transmitted over the same link. Therefore, the inability to form the EtherChannel is not due to the mode of the member interfaces.

Practice this question →

PBQhard

You are connected to SW1. The current configurations of interfaces GigabitEthernet0/1 and GigabitEthernet0/2 are as follows: Gi0/1: speed 100, duplex half, switchport access vlan 10 Gi0/2: speed 1000, duplex full, switchport access vlan 20 The port-channel interface 1 does not exist. Configure a LACP EtherChannel between SW1 and SW2 using these two interfaces, with port-channel 1 and mode active on both sides. Ensure the channel forms by resolving any speed/duplex or VLAN mismatches. After configuration, verify with 'show etherchannel summary'.

Network Topology

Hints

•Check speed and duplex consistency between member interfaces.
•All member interfaces must be in the same VLAN.
•The port-channel interface VLAN must match the physical interfaces.

A.The EtherChannel will not form because the physical interfaces have mismatched speed/duplex and VLAN assignments. You must configure both interfaces with the same speed (1000), duplex (full), and access VLAN (10), then apply channel-group 1 mode active on each.

B.The EtherChannel will form successfully because LACP active mode negotiates the channel regardless of speed/duplex or VLAN differences.

C.The EtherChannel will not form because the port-channel interface must be configured with the same VLAN as the physical interfaces, but the physical interfaces can have different speeds.

D.The EtherChannel will form successfully because the port-channel interface inherits the VLAN from the first physical interface added, so no additional configuration is needed.

AnswerA

solution

! SW1
interface GigabitEthernet0/1
speed 1000
duplex full
switchport access vlan 10
channel-group 1 mode active
interface GigabitEthernet0/2
speed 1000
duplex full
switchport access vlan 10
channel-group 1 mode active
interface Port-channel1
switchport access vlan 10

Why this answer

The EtherChannel fails because member interfaces have mismatched speed/duplex (Gi0/1 is 100/half, Gi0/2 is 1000/full) and different VLANs (VLAN 10 vs 20). Additionally, the port-channel interface and physical interfaces must have matching VLAN assignments. To fix, unify both physical interfaces to the same speed (1000), duplex (full), and access VLAN (10).

Then set channel-group mode active on each physical interface. Finally, ensure the port-channel interface also uses VLAN 10. Verify with 'show etherchannel summary' which should show the port-channel as SU (in use).

Exam trap

Cisco exam traps often test the requirement for identical speed, duplex, and VLAN on all EtherChannel member interfaces. Do not assume LACP can negotiate mismatches; it only handles aggregation, not physical or VLAN parameters.

Why the other options are wrong

LACP active mode only enables negotiation, but it does not resolve underlying parameter mismatches. The interfaces must still have consistent speed, duplex, and VLAN configuration.

All member interfaces must have identical speed and duplex settings. Even if VLANs match, speed mismatch will cause the channel to fail.

The port-channel interface is a logical interface that requires its own VLAN configuration. Physical interfaces must have identical VLAN assignments; otherwise, the channel will not form.

Practice this question →

MCQhard

Refer to the exhibit. A network engineer notices that on a four-link EtherChannel bundle between two switches, all traffic from a particular VLAN is being forwarded over only one physical link, while the other three links remain idle. The engineer suspects a load-balancing issue and issues the show etherchannel load-balance command, the output of which is shown. What is the most likely cause of the uneven traffic distribution?

A.The switch is using source‑MAC‑address load balancing, and multiple end hosts are appearing with the same source MAC address.

B.The EtherChannel is misconfigured with an LACP active/passive mode mismatch, forcing only one link to bundle.

C.VLAN pruning on the trunk has removed the VLAN from three of the four member interfaces.

D.Spanning Tree Protocol has blocked three of the four links in the EtherChannel because they form a loop.

AnswerA

The show etherchannel load-balance output confirms the global load‑balancing method is src‑mac. With this method, frames with an identical source MAC always hash to the same physical member link, causing all traffic from hosts sharing that MAC to use only one link.

Why this answer

The output of 'show etherchannel load-balance' indicates the switch is using source-MAC-address load balancing. With this method, all frames from a given source MAC address are hashed to the same physical link. If multiple end hosts in the VLAN are actually behind a single upstream router or firewall that uses the same source MAC address for all traffic (e.g., due to proxy ARP or NAT), then all traffic from that VLAN will be pinned to one link, leaving the other three idle.

Exam trap

Cisco often tests the misconception that load-balancing issues are caused by misconfiguration or STP, when the real problem is the hash algorithm's behavior with a single dominant source MAC address.

Why the other options are wrong

Candidates may think that an LACP problem explains a single active link, but a mismatch would cause the entire EtherChannel to fail, not selectively use one member.

Candidates might mistake an idle member for a pruned VLAN, but pruning would not affect all traffic, only the specific VLAN, and it is not related to the load‑balance method shown.

Candidates may associate an idle link with STP blocking, but an EtherChannel bundle presents one logical link to STP. A blocking state on some members only would indicate a serious configuration error, not the load‑balance method shown.

Practice this question →

MCQmedium

An administrator configures an EtherChannel between SW1 and SW2. The port-channel interfaces are physically up, but the EtherChannel bundle fails to come up. On SW1, the channel-group is set to mode active; on SW2, it is set to mode on. What is the most likely cause?

A.The switch priority values are mismatched

B.One side is using LACP active while the other side is set to on

C.The native VLAN must be VLAN 1 for EtherChannel to form

D.Gi1/0/2 cannot be bundled because interfaces must be in different VLANs

AnswerB

The EtherChannel fails because LACP active mode actively sends LACPDUs to negotiate a bundle, but the opposite side configured with mode on is a static EtherChannel that performs no dynamic negotiation. Since mode on ignores LACP advertisements, the negotiation handshake never completes, leaving both links in their default non-bundled state. To form the bundle, both sides must use either LACP active/passive or both be set to the same static on mode.

Why this answer

EtherChannel requires compatible modes: LACP active mode sends negotiation packets, while 'on' mode disables all negotiation, so the two sides cannot agree and the bundle stays down. Option A is wrong because switch priority values are used in STP root election, not EtherChannel formation. Option C is wrong because the native VLAN does not need to be VLAN 1; it only needs to match on both ends.

Option D is wrong because all member interfaces in an EtherChannel must be in the same VLAN, not different ones.

Exam trap

Ensure both sides of an EtherChannel are set to compatible modes; 'on' mode does not participate in LACP negotiation.

Why the other options are wrong

Switch priority values affect STP root bridge election, not EtherChannel formation. EtherChannel negotiation depends on the channel-group mode (LACP, PAgP, or on), not on switch priority.

EtherChannel does not require native VLAN to be VLAN 1; it can form with any native VLAN as long as both sides match. The issue here is the LACP mode mismatch (active vs. on), not the native VLAN.

EtherChannel does not require interfaces to be in different VLANs; in fact, all interfaces in a bundle must belong to the same VLAN or be configured as trunk ports with the same allowed VLAN list. Option D is incorrect because bundling interfaces in different VLANs would cause a mismatch.

Practice this question →

MCQmedium

Two switches are configured to form an EtherChannel, but the bundle never comes up. Which explanation best describes this scenario?

A.The switches are using different native VLANs.

B.LACP active on one side is incompatible with mode on on the other side.

C.Both sides must use PAgP desirable mode.

D.The interfaces must be configured as routed ports first.

AnswerB

LACP active mode actively sends LACPDUs to negotiate the bundle, while 'mode on' forces the channel statically without sending any negotiation frames. Because the 'on' side never responds to LACP, the active side cannot establish a working partner and the EtherChannel fails to form. The mismatch is a fundamental protocol/config mode incompatibility, not a wiring or VLAN issue.

Why this answer

One side is using LACP active mode and the other side is forcing a static channel-group with mode on. Those modes are not compatible. LACP needs active or passive on both sides, while PAgP uses desirable or auto, and static mode on expects a manual bundle on the other side.

Exam trap

Ensure you match the correct protocol and mode on both sides of the link; mixing protocols or incompatible modes will prevent channel formation.

Why the other options are wrong

This option is wrong because different native VLANs do not prevent an EtherChannel from forming; they can still establish a link if other configurations are compatible. The primary issue in this scenario is related to LACP mode mismatches.

This option is incorrect because EtherChannel can use either PAgP or LACP for negotiation, and both protocols can operate independently of each other. The requirement for both sides to use PAgP in desirable mode is not a necessity for EtherChannel to function.

This option is wrong because EtherChannel can be configured on switch ports without needing to convert them to routed ports. Routed ports are not necessary for EtherChannel to function, as it operates at Layer 2.

Practice this question →

MCQhard

A network engineer has configured an LACP EtherChannel between Switch1 and Switch2 by assigning interfaces to channel-group 1 with the mode passive on both switches. The engineer issues the show etherchannel summary command on Switch1 and sees the output below. The Port-channel interface remains down. Which action resolves the issue?

A.Configure the switchport mode as trunk on both sides.

B.Change the mode on one switch to active.

C.Verify that the native VLAN matches on both sides of the trunk.

D.Correct the speed and duplex settings on the member ports.

AnswerB

In LACP, passive mode interfaces only respond to received PDUs; they never initiate LACP negotiation. Since both switches are configured with passive mode, no LACP PDUs are exchanged, and the ports remain in a standalone (I) state. Changing one switch to active makes it actively send LACP PDUs, which prompts the passive peer to reply and complete the negotiation, allowing the member ports to bundle into the Port-channel. This directly fixes the root cause of the failure.

Why this answer

When both switches are configured with LACP mode passive, neither switch initiates the negotiation process because passive mode only responds to incoming LACP packets. By changing one side to active mode, that switch will actively send LACP packets, allowing the EtherChannel to form. The Port-channel interface remains down due to this negotiation failure, not because of VLAN or physical mismatch issues.

Exam trap

Cisco often tests the LACP mode interaction by setting both sides to passive, leading candidates to incorrectly focus on trunking, VLAN, or physical layer issues instead of recognizing that LACP requires at least one side to be active.

Why the other options are wrong

The show output indicates Layer 2 mode is already active, and trunking isn’t required for bundling. The issue is LACP protocol negotiation, not interface mode.

The Port-channel would still form even with a native VLAN mismatch; it would not be down (SD) and ports would not be stand-alone (I) solely because of VLAN mismatch.

The flags in the output (I, SD) are not consistent with a speed/duplex problem, and the explicit configuration of passive mode on both sides is the known root cause.

Practice this question →

MCQhard

Refer to the exhibit. A network engineer is troubleshooting an EtherChannel on R1 that is not passing traffic. The output of the show etherchannel summary command is displayed. What is the most likely cause?

A.The local switch is configured with LACP passive while the remote switch is set to LACP active.

B.One side is configured with LACP active and the other side is configured with mode 'on' (static).

C.The remote switch is configured with PAgP desirable while the local switch uses LACP.

D.The port-channel member interfaces are configured as access ports, preventing LACP from negotiating.

AnswerB

With LACP active on one side and mode 'on' on the fabric peer, the 'on' port forces an EtherChannel statically and never transmits LACP PDUs, so the active LACP port never receives a response and cannot move the member port to a bundled state. The port-channel interface may still be administratively up and declared up (SU) because it exists in configuration, but the physical member ports remain in a down (D) state because no LACP negotiation completed. This exact combination produces the (D) flags on member ports while the port-channel itself remains up, making it the correct cause.

Why this answer

The 'show etherchannel summary' output shows the port-channel is down (flags indicate 'D' for down), and the most common cause when one side is configured with LACP active and the other with mode 'on' (static) is a protocol mismatch. LACP active expects to negotiate with another LACP-enabled port, but static mode 'on' forces the link up without negotiation, causing the EtherChannel to fail to form. This mismatch prevents the exchange of LACP frames, leaving the bundle in an error-disabled or non-functional state.

Exam trap

Cisco often tests the misconception that LACP passive/active is incompatible, but the real trap is confusing static mode 'on' (which disables negotiation) with LACP modes, leading candidates to overlook the protocol mismatch between LACP and static configuration.

Why the other options are wrong

LACP passive is not incompatible with LACP active.

PAgP/LACP mismatch leads to suspended state, not down; the exhibit's (D) indicates the link is not up, which points to LACP negotiation failure rather than protocol mismatch.

LACP negotiation is independent of the access/trunk configuration.

Practice this question →