CCNP Architecture Practice Question
A network engineer is designing a high-availability campus network using Cisco StackWise Virtual. The engineer wants to ensure that if the virtual link fails, the switches do not both become active and cause a split-brain scenario. Which mechanism should be implemented to detect and prevent a dual-active situation?
⚠ Common exam trap
A common mix-up: candidates confuse dual-active detection with other protocols like PAgP, VRRP, or BFD, which serve different purposes and do not prevent a split-brain in StackWise Virtual.
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 a separate physical link as a dual-active detection link and enable dual-active detection.
StackWise Virtual uses a dual-active detection link to prevent a split-brain scenario. This is a separate physical link between the two switches that is used to detect a virtual link failure. When the virtual link fails, the switches communicate over the dual-active detection link to determine which switch should remain active. Configuring this link and enabling dual-active detection is the correct approach.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable PAgP on the virtual link to detect dual-active condition.
Why it's wrong here
PAgP is a Cisco proprietary EtherChannel protocol used for link aggregation, not for dual-active detection. The virtual link in StackWise Virtual uses a different mechanism for dual-active detection. Using PAgP would not provide the necessary detection and could interfere with the virtual link operation. Dual-active detection requires a dedicated link and configuration.
- ✗
Enable BFD on the virtual link to rapidly detect failures.
Why it's wrong here
BFD (Bidirectional Forwarding Detection) is used for fast failure detection of routing protocols and links, but it is not the mechanism used for dual-active detection in StackWise Virtual. While BFD can detect link failures quickly, it does not provide the specific dual-active detection and resolution that StackWise Virtual requires. A dedicated dual-active detection link is needed.
- ✗
Configure VRRP on the switches to monitor the virtual link.
Why it's wrong here
VRRP is a first-hop redundancy protocol that provides gateway redundancy, not dual-active detection for StackWise Virtual. VRRP operates at the network layer and does not monitor the virtual link or the StackWise Virtual control plane. Using VRRP would not prevent a dual-active scenario; it is unrelated to the mechanism required.
- ✓
Configure a separate physical link as a dual-active detection link and enable dual-active detection.
Why this is correct
In StackWise Virtual, a dual-active detection link is a separate physical connection between the two switches that is used to detect a virtual link failure. When the virtual link fails, the switches use this link to determine which switch should remain active. Configuring this link and enabling dual-active detection prevents both switches from becoming active and causing a split-brain.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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