The Firewall Loop LACP Missed: Why Network Topology Validation Matters

This incident exposes LACP's inability to detect Layer 2 loops when hardware is misconfigured in redundant setups. Purely metric-based monitoring missed the silent failure—only traffic asymmetry analysis revealed the root cause (firewall connected to both switches via port-channels). It demonstrates why topology validation is essential during infrastructure deployments to prevent cascading protocol failures.