A significant internet outage impacted users in Iceland, Spain, and Portugal on November 27, 2023, attributed to a Border Gateway Protocol (BGP) routing leak. The incident, which began around 10:20 UTC and was largely resolved by 11:15 UTC, caused widespread connectivity issues, particularly affecting the Icelandic government network and various internet service providers (ISPs) in the Iberian Peninsula.
The BGP leak originated from an Icelandic ISP, Snerpa, which inadvertently advertised routes for approximately 17,000 IP prefixes belonging to other networks. This misconfiguration caused internet traffic destined for these prefixes to be rerouted through Snerpa's network, leading to severe congestion and dropped connections. The affected prefixes included those belonging to major ISPs in Spain and Portugal, as well as critical infrastructure in Iceland.
Monitoring services observed a dramatic increase in announced BGP routes from Snerpa during the incident, peaking at over 17,000 additional prefixes. This surge in advertisements, which included routes for networks in Spain, Portugal, and other regions, indicated a broad routing misdirection. The incident was quickly detected by network operators and internet monitoring platforms due to the sudden and unusual routing changes.
The Icelandic government confirmed that its network experienced disruptions as a direct result of the BGP leak. Several government websites and online services became inaccessible for a period. In Spain and Portugal, numerous ISPs reported significant service interruptions, with customers unable to access various online resources. The impact was particularly noticeable for services relying on the misdirected IP ranges.
Network engineers and cybersecurity analysts noted that BGP leaks, while often accidental, can have far-reaching consequences due to the internet's decentralized routing architecture. Such incidents highlight the importance of robust BGP security measures, including route filtering and RPKI (Resource Public Key Infrastructure) validation, to prevent the propagation of erroneous routing information. While the incident was resolved relatively quickly, it underscored the fragility of global internet routing and the potential for a single misconfiguration to cause widespread disruption.
