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Difficulty: MediumLayer 2 and Layer 3 EtherChannel (LACP)

A network engineer is configuring a Layer 3 EtherChannel between two Cisco switches using Link Aggregation Control Protocol (LACP). Which two actions or configurations are required to ensure the EtherChannel forms successfully and routes IP traffic correctly? (Choose two.)

  1. Assign the IP address directly to the logical port-channel interface after configuring it as a routed interface using the no switchport command.Answer
  2. Configure the channel-group mode as active on one switch and passive on the opposing switch.Answer
  3. C
    Configure the channel-group mode as passive on both interconnected switches.
  4. D
    Configure the channel-group mode as desirable on one switch and active on the opposing switch.

Answer

The correct configurations are assigning the IP address directly to the logical port-channel interface (configured with the no switchport command) and matching an active LACP mode on one switch with a passive LACP mode on the opposing switch.
Layer 3 EtherChannels require IP addresses to be assigned to the logical port-channel interface configured with 'no switchport'. For dynamic LACP bundle creation, at least one switch must be set to active mode while the opposing switch can be passive.

Step-by-Step Solution

1
Identify Layer 3 interface and IP addressing requirements for EtherChannel
Logical Port-Channel interface must have switchport capabilities removed ('no switchport') and receive the IP address assignment.
Layer 3 routing decisions occur at the aggregate logical interface level rather than on individual physical member ports.
2
Evaluate LACP negotiation mode compatibility matrix
Active-passive and active-active pairings form an EtherChannel bundle, whereas passive-passive pairings fail.
At least one side of the link aggregation bundle must actively transmit LACP frames to begin dynamic negotiation.
3
Verify protocol alignment between switches
PAgP modes (desirable/auto) cannot pair with LACP modes (active/passive).
Both endpoints must agree on the underlying aggregation protocol (LACP vs PAgP) for bundle negotiation to succeed.

Key Concept

Layer 3 EtherChannel Configuration and LACP Mode Negotiation
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Topics

Layer 2 and Layer 3 EtherChannel (LACP)

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