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Difficulty: MediumLayer 2 and Layer 3 EtherChannel (LACP)

A network administrator is connecting Switch-1 and Switch-2 using a dual-link EtherChannel across GigabitEthernet0/1 and GigabitEthernet0/2 interfaces. On Switch-1, the member interfaces are configured with `channel-group 10 mode active`. What will happen if the corresponding physical interfaces on Switch-2 are configured with `channel-group 10 mode passive`?

  1. The EtherChannel bundle will successfully form because active mode actively initiates LACP negotiation while passive mode responds to incoming LACP packets.Answer
  2. B
    The EtherChannel bundle will fail to form because both participating switches must be configured in active mode to negotiate LACP.
  3. C
    The interfaces will automatically fall back to PAgP desirable mode to complete port-channel aggregation.
  4. D
    The port-channel interface will become error-disabled due to a protocol encapsulation mismatch.

Answer

The EtherChannel bundle will successfully form because active mode actively initiates LACP negotiation while passive mode responds to incoming LACP packets.
Link Aggregation Control Protocol (IEEE 802.3ad / 802.1AX) uses active and passive negotiation modes. The active keyword causes the switch port to actively initiate negotiation by transmitting LACP packets. The passive keyword configures the port to respond to received LACP packets without sending them unprompted. Therefore, combining an active port on one side with a passive port on the other side successfully forms an EtherChannel.

Step-by-Step Solution

1
Analyze Switch-1's LACP mode configuration.
Switch-1 is set to 'active', meaning it sends LACP frames out of the interfaces to negotiate the bundle.
LACP active mode actively initiates link aggregation negotiations.
2
Analyze Switch-2's LACP mode configuration.
Switch-2 is set to 'passive', meaning it does not initiate LACP negotiation but responds when it receives LACP frames.
LACP passive mode listlessly waits for received LACP packets before forming an EtherChannel.
3
Determine the resulting channel negotiation status.
Active mode sends LACP frames, passive mode receives and responds to them, allowing the bundle to successfully form.
Active-to-Active and Active-to-Passive combinations establish LACP EtherChannels, whereas Passive-to-Passive fails.

Key Concept

LACP EtherChannel Negotiation Modes (Active and Passive)
Estimated Time:1m 30s
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Topics

Layer 2 and Layer 3 EtherChannel (LACP)

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