After a network audit, a network engineer must optimize the current network convergence time. The proposed solution must consider link layer and control plane failures. Which solution meets the requirements?
To achieve subsecond convergence in IS-IS or OSPF networks and quickly detect both:
Link-layer failures (e.g., interface flaps)
Control-plane adjacency loss
The best solution is:
C. BFD (Bidirectional Forwarding Detection): A lightweight protocol that enables subsecond failure detection, independent of the IGP timers, by establishing fast detection sessions over forwarding paths.
This is widely deployed in high-performance networks to accelerate convergence without compromising routing stability.
Why other options fall short:
A. Debounce timers delay interface-down events (not suitable when fast detection is required).
B. Fast hellos affect hello interval but are still slower and CPU-intensive.
D. LSP fast flood improves LSP propagation but doesn’t address failure detection speed.
This solution is central to CCDE “Protocol Design Implications” where rapid failure detection and recovery drive the convergence architecture.
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