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Difficulty: EasyLayer 2 and Layer 3 EtherChannel (LACP)

A network technician is setting up dynamic link aggregation using Link Aggregation Control Protocol (LACP) between two Cisco switches. Which TWO channel-group mode pairings will successfully establish an operational EtherChannel bundle? (Select two.)

  1. Both switch interfaces configured in active modeAnswer
  2. One switch interface configured in active mode and the other in passive modeAnswer
  3. C
    Both switch interfaces configured in passive mode
  4. D
    One switch interface configured in active mode and the other in desirable mode

Answer

The correct options are configuring both interfaces in active mode, and configuring one interface in active mode with the opposing interface in passive mode.
LACP EtherChannel formation requires at least one participating interface to be in active mode to send LACP frames. Thus, active-active and active-passive combinations will both form a functional bundle.

Step-by-Step Solution

1
Analyze LACP operational modes.
Active mode actively transmits LACP packets, whereas passive mode only responds to received LACP packets.
At least one endpoint must be configured in active mode to initiate the LACP packet exchange.
2
Evaluate protocol compatibility.
Desirable mode belongs to PAgP, which is incompatible with LACP.
Both switches must use matching aggregation protocols (LACP to LACP or PAgP to PAgP).

Key Concept

LACP Mode Negotiation Dynamics
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Topics

Layer 2 and Layer 3 EtherChannel (LACP)

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