Troubleshooting LACP Mode Mismatch in vSphere Distributed Switch
A large financial organization has a vSphere cluster with 10 ESXi hosts (8.x) connected to a pair of Nexus 9000 switches via two 10G LACP link aggregation groups (LAGs) per host. Each host has a vSphere Distributed Switch (vDS 7.0.3) with two LAGs (LAG1: vmnic0, vmnic1; LAG2: vmnic2, vmnic3). The vDS has three port groups: Production (VLAN 100-200), DMZ (VLAN 300), and Storage (VLAN 400). The port groups use LACP with load balancing 'Route based on IP hash'. Recently, the network team changed the physical switch port channels from mode 'active' to 'passive' on the downstream ports connected to host #3, without informing the virtualization team. Within hours, VMs on host #3 experience intermittent connectivity; some can communicate but others cannot, and vMotion between host #3 and other hosts fails with a network unreachable error. iSCSI storage traffic from host #3 is also unstable. The administrator verifies that the vDS LACP configuration on host #3 still expects 'active' mode. Which of the following actions is the most effective to restore full functionality while maintaining LACP?
Quick Answer
The answer is to remove and recreate the LAGs on host #3’s vDS after verifying the physical switch’s LACP configuration. This is correct because an LACP mode mismatch—where the vDS expects active but the physical switch is now passive—can still form a link if one side initiates negotiation, but the real failure often stems from mismatched LAG identifiers or port-channel parameters that a simple mode change won’t fix. Recreating the LAGs forces a fresh LACP negotiation with synchronized settings, ensuring the vDS and Nexus 9000 agree on port membership and hashing. On the VCP-DCV exam, this scenario tests your understanding that LACP troubleshooting requires end-to-end consistency; a common trap is assuming active-passive always works, but passive-passive fails silently, and mismatched LAG IDs cause intermittent connectivity. Remember the mnemonic: “Match the mode, sync the ID—recreate to guarantee harmony.”
⚠ Common exam trap
Watch out — candidates often assume changing the vDS LACP mode to passive (Option A) will fix the mismatch, but they overlook that passive-passive pairs never form a LAG, resulting in no link aggregation at all.
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
✓
Remove and recreate the LAGs on host #3's vDS after verifying the physical switch's LACP configuration.
The root cause is a mismatch between the vDS LACP mode (active) and the physical switch's LACP mode (passive). Simply recreating the LAGs after verifying the switch configuration ensures both sides agree on the LACP mode, restoring proper negotiation and traffic flow. This maintains the existing LACP-based load balancing and avoids disrupting the rest of the cluster.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Change the LACP mode on host #3's vDS from 'active' to 'passive' for both LAGs.
Why it's wrong here
Changing to passive would cause both ends to be passive, preventing LACP negotiation, making the problem worse.
- ✗
Disable LACP on host #3's vDS and use static EtherChannel instead.
Why it's wrong here
This would require physical switch reconfiguration and does not maintain LACP, violating the 'maintaining LACP' requirement.
- ✗
Replace the vDS with multiple standard switches and use active/standby failover.
Why it's wrong here
This is a major architectural change that is unnecessary and would not maintain LACP, nor is it quick.
- ✓
Remove and recreate the LAGs on host #3's vDS after verifying the physical switch's LACP configuration.
Why this is correct
Recreating the LAGs on the vDS, after verifying the physical switch's LACP settings, ensures LAG IDs and modes are synchronized, restoring LACP functionality.
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Same concept, more angles
2 more ways this is tested on VCP-DCV
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which THREE of the following are prerequisites for configuring LACP on a vSphere Distributed Switch? (Select exactly three.)
medium- ✓ A.The vSphere Distributed Switch must be configured with enhanced LACP support.
- B.Each uplink must be in a separate VLAN to avoid loops.
- ✓ C.The physical switch ports must be configured as LACP active or passive.
- D.The uplinks must be connected to different physical switches for redundancy.
- ✓ E.The physical network switch must support LACP (IEEE 802.3ad).
Why A: Options A, C, and E are correct. For LACP on a vSphere Distributed Switch, the vDS must be configured with enhanced LACP support (option A). The physical switch ports must be configured for LACP, either in active or passive mode (option C). Additionally, the physical network switch must support LACP (IEEE 802.3ad) (option E). Option B is incorrect because each uplink does not need to be in a separate VLAN; LACP works across VLANs and VLAN configuration is independent. Option D is incorrect because the uplinks must be connected to the same physical switch to form a LAG; using different switches requires Multi-chassis LACP (e.g., MLAG).
Variation 2. An ESXi host has two physical uplinks (vmnic0, vmnic1) connected to a distributed switch. The administrator wants to use LACP to aggregate these uplinks to a physical switch stack. Which prerequisite must be met for LACP to work with a distributed switch?
hard- A.The physical switch must be configured with a static LAG.
- B.The distributed switch version must be 5.5 or later.
- C.The uplinks must be in an active/standby configuration.
- ✓ D.The distributed switch must be configured with a LAG and the physical switch with matching LACP settings.
- E.The LACP group must have a unique MAC address.
Why D: For LACP to work with a distributed switch, the distributed switch must be configured with a Link Aggregation Group (LAG) and the physical switch must be configured with matching LACP settings. Option A is incorrect because LACP requires a dynamic LAG on the physical switch, not static. Option B is incorrect because LACP support for distributed switches was introduced in vSphere 5.1, not 5.5. Option C is incorrect because LACP requires active/active configuration, not active/standby. Option E is not a prerequisite; LACP uses the physical MAC addresses of the uplinks.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This VCP-DCV practice question is part of Courseiva's free VMware 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 VCP-DCV exam.