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Zorluk: OrtaLayer 2 and Layer 3 EtherChannel (LACP)

A network administrator executes the command `show etherchannel summary` on a Cisco switch to troubleshoot a newly configured EtherChannel link. The output displays the following information:

text Flags: D - down P - bundled in port-channel I - stand-alone s - suspended H - Hot-standby (LACP only) S - Layer2 U - in use Group Port-channel Protocol Ports ------+--------------+---------+----------------------------------------------- 1 Po1(SU) LACP Gi0/1(I) Gi0/2(I)

Based on the output, which configuration state is the primary cause of both physical member interfaces remaining in the `(I)` stand-alone state?

  1. Both interconnecting switches have their physical member interfaces configured in LACP passive mode.Cevap
  2. B
    The local switch is configured in LACP active mode, while the remote switch is configured in LACP passive mode.
  3. C
    The physical member interfaces on the local switch have mismatched native VLAN configurations.
  4. D
    The local switch is configured for LACP active mode, while the remote switch is configured for PAgP desirable mode.

Cevap

Both interconnecting switches have their physical member interfaces configured in LACP passive mode.
In LACP negotiation, an interface configured in passive mode will listen for LACP packets but will never initiate transmission of LACP PDUs. If both switches across a link are set to passive mode, neither switch sends LACP packets. Consequently, LACP negotiation never completes, and member interfaces remain in the stand-alone state indicated by the flag (I) in the show etherchannel summary output.

Adım Adım Çözüm

1
Analyze the output of the show etherchannel summary command
Port-channel status is SU (Layer 2, in use), protocol is LACP, but member ports GigabitEthernet0/1 and GigabitEthernet0/2 are marked with flag (I).
According to the output flags, (I) indicates stand-alone mode, meaning the physical interfaces are operating independently and have not successfully negotiated into the bundled channel group.
2
Evaluate LACP mode negotiation mechanics
LACP supports two modes: active (initiates negotiation by sending LACP PDUs) and passive (responds to LACP PDUs but does not initiate them).
At least one side of the link must be set to active mode to initiate the exchange of LACP packets.
3
Identify the cause of stand-alone state
When both sides are configured as passive, neither switch initiates LACP PDU exchange. As a result, LACP negotiation fails to start, leaving member ports in the stand-alone (I) state.
Matching passive-passive modes fail to negotiate an operational EtherChannel.

Anahtar Kavram

LACP Mode Negotiation and Verification Flags
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Konular

Layer 2 and Layer 3 EtherChannel (LACP)

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