Bgp Route Flapping

Why BGP Route Flapping Still Keeps Me Up at Night

Back when I was at Juniper handling support calls from ISPs, route flapping was the ghost in the machine that nobody wanted to talk about. You’d get these periodic convergence storms where a single misbehaving router would trigger cascading updates across an entire autonomous system. The worst part wasn’t the initial flap - it was the echo effect, where dampening algorithms would actually make things worse by creating these weird oscillation patterns that looked almost biological in their rhythm.

The real killer is that most network engineers treat route flapping like they treat dental work - they know it’s important but they’d rather not think about it until something’s on fire. I learned this the hard way at 2 AM when a major backbone provider called in because their entire West Coast presence was doing the BGP equivalent of a cardiac arrhythmia. Turns out they’d set their MRAI timers too aggressively and created a perfect storm where every update triggered three more updates in this beautiful exponential explosion.

These days when I see people deploying SDN solutions without understanding the fundamentals of route stability, I get this little twitch in my left eye. Sure, your overlay network is pretty, but what happens when your underlay starts flapping? The physics of distributed systems doesn’t care about your abstraction layers. Route flapping is like entropy - you can’t eliminate it, you can only move it around and hope it lands somewhere less critical.