Following my article on Loop-Free Alternate Routes, Michael McNamara made a good point about some of the issues detecting failure in a Metro Ethernet network. This seems to be a commonly misunderstood problem.
Whilst at Cisco Live recently I was intrigued to learn about an apparently simple yet effective fast routing convergence technique called Loop-Free Alternate Fast ReRoute (LFA-FRR), a.k.a. IP Fast ReRoute (IP-FRR).
Many service providers and enterprises these days tune their interior gateway protocol (IGP) timers, aiming to achieve sub-200ms convergence. This can be quite an intensive and design impacting challenge.