A Routing Bug Took Solana 86% of the Way to Losing Finality

In brief

• Almost 29% of staked SOL went delinquent early Wednesday after a routing fault at hosting provider Teraswitch, against the 33% at which Solana stops finalizing blocks.
• One network, AS20326, holds some 27% of staked SOL, above the 25% cap the Solana Foundation's delegation program sets, and 94% of it went dark at once.
• Around 90 validators were affected, losing a combined 333 SOL in rewards.

Solana came within 4.51 percentage points of losing the ability to finalize transactions on Wednesday morning, after a single misconfigured route at one hosting provider knocked 28.83% of staked SOL offline. The chain stops finalizing at 33.34%, meaning the network got roughly 86% of the way there.

Teraswitch, the provider, has published a writeup explaining how it happened. The company uses a default route internally to signal that an edge router can reach the internet, with each site normally preferring the one its own routers originate. A default route from its Miami site was propagated with its metric and communities stripped, and a route reflector in Amsterdam pushed it into Europe and Asia-Pacific.

Edge routers there read it as locally originated and preferred it over their real one, then passed it to the data center core, which rejected it as invalid. Twelve sites in London, Amsterdam, Dublin, Frankfurt, Singapore and Tokyo were left with nothing valid to forward to. North America was untouched. Engineers found the fault within ten minutes and service returned at 04:16:15 UTC.