Troubleshooting MACsec Operational Down on Cloud Interconnect
You work for a large organization that recently implemented a 100GB Cloud Interconnect connection between your Google Cloud and your on-premises edge router. While routinely checking the connectivity, you noticed that the connection is operational but there is an error message that indicates MACsec is operationally down. You need to resolve this error. What should you do?
Community Votes
100% of anonymous learners picked answer D. Votes are pick records left by other test-takers — they are not the verified answer.
Community Insight
Tests MACsec authentication requirements, with the common trap being confusion between key expiration and key mismatch during initial setup.
This question tests troubleshooting MACsec session failures on Google Cloud Interconnect by verifying endpoint authentication. It establishes that mismatched pre-shared keys are the primary cause of an operationally down MACsec state.
Candidates often choose C (key expiration) instead of D (key mismatch), overlooking that a newly provisioned link will fail immediately if the configured PSKs do not align exactly on both routers.
Community Discussion (4 comments)
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Expert Analysis
Why the Answer Is Correct
MACsec relies on identical cryptographic keys at both endpoints to negotiate a secure data plane. When the active pre-shared key (PSK) configured on the on-premises router differs from the one set on Google’s edge router, the MACsec association fails to establish, resulting in an operationally down status. Verifying and aligning these keys restores the encrypted tunnel.Why the Other Options Are Wrong
Option A is incorrect because the connection is already provisioned and operational at Layer 2/3, meaning MACsec support is inherently available. Option B contradicts the prompt, which explicitly states the underlying connectivity is up. Option C focuses on key expiration, which is highly improbable for a freshly deployed interconnect and is secondary to the fundamental requirement of key parity during initial negotiation.Community Comment Notes
Learners consistently validate D by referencing official troubleshooting documentation that lists key mismatches as a primary failure mode. BondleB shared the direct vendor troubleshooting page confirming this behavior. Several users noted that since this is a new deployment, expiration (Option C) is unrealistic compared to configuration alignment. Multiple commenters confirmed that matching the PSKs directly resolves the operational down state without requiring additional policy changes.Official Reference
Exam Strategy
When troubleshooting security features like MACsec or IPsec, always verify cryptographic alignment first. Mismatched keys, algorithms, or lifetimes are the most frequent causes of negotiation failures, especially on newly provisioned links.
Frequently Asked Questions
Why is key expiration (C) incorrect for a new MACsec setup?
Expiration applies to long-running deployments; a newly provisioned link fails immediately due to configuration mismatch, making alignment the priority.
Can MACsec be operationally down if the underlying VLAN is up?
Yes. MACsec operates at Layer 2 for encryption and authentication, negotiating independently of the base transport path status.