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Difficulty: EasyLayer 2 and Layer 3 EtherChannel (LACP)

A network administrator is connecting two Cisco Catalyst switches using an IEEE 802.3ad Link Aggregation Control Protocol (LACP) EtherChannel. SwitchA has its member interfaces configured with the command `channel-group 1 mode passive`. Which mode must be configured on SwitchB's corresponding member interfaces to successfully form the EtherChannel?

  1. activeAnswer
  2. B
    passive
  3. C
    desirable
  4. D
    auto

Answer

The mode 'active' must be configured on SwitchB.
The correct answer specifies 'active' mode. In LACP, 'active' mode actively sends LACP negotiation frames, whereas 'passive' mode only listens and responds. Because the remote switch is set to 'passive', the local switch must be set to 'active' to initiate communication and successfully build the bundle.

Step-by-Step Solution

1
Identify the protocol associated with the configured mode.
The command 'mode passive' indicates the use of Link Aggregation Control Protocol (LACP), an open standard protocol.
EtherChannel negotiation protocols (LACP vs PAgP) cannot be mixed.
2
Analyze the operational state of LACP 'passive' mode on SwitchA.
SwitchA is in a passive state, meaning it will listen and respond to incoming LACP packets but will not initiate negotiation.
Two passive switches will wait indefinitely for the other to start negotiation, keeping the link down.
3
Determine the required mode for SwitchB.
SwitchB must be set to 'active' mode so that it actively transmits LACP packets to initiate channel creation.
An LACP EtherChannel requires at least one side to actively initiate negotiation (active-active or active-passive).

Key Concept

LACP Mode Compatibility
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Topics

Layer 2 and Layer 3 EtherChannel (LACP)

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