easyMultiple Choice
CCNP Practice Question: Is configuring an EtherChannel between a Cisco…
A network engineer is configuring an EtherChannel between a Cisco switch and a server that supports LACP. The switch ports are configured as trunk ports allowing multiple VLANs. The engineer wants to ensure the EtherChannel forms automatically without manual intervention. Which configuration should be applied on the switch?
⚠ Common exam trap
Cisco often tests the distinction between LACP modes (active/passive) and PAgP modes (desirable/auto), and the trap here is that candidates confuse 'mode desirable' (PAgP) with LACP, or assume 'mode passive' is sufficient when the server might also be passive, leading to a non-forming EtherChannel.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure the port-channel with 'channel-group 1 mode active'.
'mode active' enables LACP unconditionally on the switch port, causing it to actively send LACP packets to negotiate and form an EtherChannel with the server. Since the server supports LACP, this ensures automatic formation without manual intervention, and the trunk ports will carry multiple VLANs across the aggregated link.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Configure the port-channel with 'channel-group 1 mode active'.
Why this is correct
Configuring the port-channel with 'channel-group 1 mode active' makes the switch actively transmit LACPDUs on the member link, initiating the IEEE 802.3ad negotiation with the server. Because LACP active mode reliably establishes the EtherChannel with any peer that is either active or passive, it is the safest choice when the server's exact teaming settings are unknown. This mode also allows the switch to detect and manage the bundled link using the standard LACP state machine.
- ✗
Configure the port-channel with 'channel-group 1 mode passive'.
Why it's wrong here
LACP passive mode does not initiate negotiation; it only responds to LACPDUs received from the peer. If the server is also configured with passive mode (or otherwise does not send LACPDUs first), the link will remain a normal access/trunk port and no EtherChannel will form because no side ever sends the initial packet. Even if the server is active, relying on the server to initiate is brittle and contrary to the best practice of configuring the switch to actively negotiate.
- ✗
Configure the port-channel with 'channel-group 1 mode desirable'.
Why it's wrong here
The 'desirable' keyword is a Cisco-proprietary PAgP (Port Aggregation Protocol) mode, not a valid LACP mode. PAgP uses Cisco's own protocol and is generally unsupported on non-Cisco server NICs and switches; if the server is configured for standard LACP, it will not understand PAgP messages and the channel will fail. Since the scenario calls for a standards-based LACP EtherChannel, 'desirable' is an invalid configuration.
- ✗
Configure the port-channel with 'channel-group 1 mode on'.
Why it's wrong here
The 'on' mode forcibly bundles the port into an EtherChannel without running any negotiation protocol, creating a static channel. A server running LACP will send LACPDUs that the switch completely ignores, so the server's LACP determines the channel is not operational and may fail to transmit or mark the link as down. Additionally, static 'on' mode does not participate in LACP's link monitoring and fault-detection mechanisms, which can hide link failures or cause misconfigurations.
Visual reference
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-401 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-401 exam.