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Difficulty: HardLayer 2 and Layer 3 EtherChannel (LACP)

A network engineer is configuring a routed (Layer 3) EtherChannel between two switches using LACP. The engineer issued the `no switchport` command on physical interfaces GigabitEthernet0/1 and GigabitEthernet0/2 before assigning them to channel group 1 with mode `active`. However, the bundle fails to pass routed traffic. Upon executing `show etherchannel summary`, the output displays:

text
Group Port-channel Protocol Ports
------+-------------+-----------+-----------------------------------------------
1 Po1(SD) LACP Gi0/1(I) Gi0/2(I)

Which administrative action will resolve this issue and bring the Layer 3 EtherChannel into an operational state?

  1. Issue the `no switchport` command on the logical Port-Channel 1 interface.Answer
  2. B
    Change the channel-group mode on the physical interfaces to `desirable` to force LACP negotiation.
  3. C
    Align the native VLAN configurations on GigabitEthernet0/1 and GigabitEthernet0/2 to eliminate trunking mismatches.
  4. D
    Remove the IP address from Port-Channel 1 and assign individual IP addresses directly to GigabitEthernet0/1 and GigabitEthernet0/2.

Answer

Issue the `no switchport` command on the logical Port-Channel 1 interface.
The `show etherchannel summary` command output displays `Po1(SD)`, where `S` signifies Layer 2 and `D` signifies Down. Because the physical member interfaces were configured with `no switchport`, they are operating as Layer 3 ports. LACP prevents ports from bundling if there is a mismatch between the physical member ports and the logical port-channel interface mode. Converting the Port-Channel 1 interface to Layer 3 using `no switchport` resolves the configuration mismatch and enables the LACP bundle to become operational (`Po1(RU)` or `Po1(SU)` depending on code version definitions).

Step-by-Step Solution

1
Analyze the flags in the `show etherchannel summary` output.
Flag `S` on `Po1(SD)` indicates Layer 2 operational mode, and flag `D` indicates Down. Flags `(I)` on member ports indicate Stand-alone state.
The physical ports were configured as routed ports (`no switchport`), but the logical Port-Channel interface retained its default Layer 2 switchport property.
2
Identify the underlying compatibility requirement for EtherChannel aggregation.
All physical member interfaces and the parent Port-Channel interface must share matching operational parameters, including Layer 2 vs. Layer 3 mode.
LACP will suspend member ports or keep them stand-alone if there is a Layer 2 / Layer 3 mode mismatch with the logical port-channel.
3
Determine the corrective CLI command on the logical interface.
Executing `interface Port-channel 1` followed by `no switchport` converts the logical interface to Layer 3.
Aligning the logical interface mode to Layer 3 allows LACP to bundle Gi0/1 and Gi0/2 into Po1, changing the flags to `SU` (Layer 3, in Use) and member port flags to `P` (bundled in port-channel).

Key Concept

Layer 3 EtherChannel Configuration and Operability Flags
Estimated Time:2m 0s
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Topics

Layer 2 and Layer 3 EtherChannel (LACP)

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