How the April 28, 2025, power outage in Portugal and Spain impacted Internet traffic and connectivity

Grid Failure in Iberia Cuts Internet Traffic, Disrupts Routing and Network Quality

A large-scale power outage across Portugal and Spain on April 28, 2025, beginning at 10:34 UTC, resulted in widespread disruption to Internet connectivity across both countries. The electrical grid failure halted transportation, closed businesses, and caused noticeable degradation in Internet traffic, network quality, and routing visibility. Impact was also reported in parts of France, with additional outages noted as far away as Belgium.

Initial statements from Portugal’s grid operator attributed the outage to a fault in the Spanish grid, citing "extreme temperature variations in the interior of Spain" and "anomalous oscillations" in 400 kilovolt transmission lines. The operator later retracted this explanation. Regardless of the root cause, the impact on Internet infrastructure was immediate and significant, as observed through traffic patterns, DNS resolver queries, bandwidth metrics, and routing announcements.

Impact on Portuguese Networks

In Portugal, country-level Internet traffic dropped sharply when power failed, falling by 50% compared with the previous week within the first hour and declining to roughly 90% below baseline over the following five hours. Traffic to Cloudflare’s 1.1.1.1 DNS resolver showed a similar pattern, initially dropping by 40% and continuing to fall in subsequent hours.

Key providers including NOS, Vodafone, MEO, and NOWO saw their traffic volumes evaporate as the outage progressed. However, MEO’s mobile network—operated under a separate autonomous system (ASN AS42863)—demonstrated an opposite trend initially. Mobile request traffic from MEO-MOVEL more than doubled as subscribers sought information about the outage, before dropping to roughly half of the previous week's volume over the following hours.

Regional traffic data shows the scope of the outage was unevenly distributed. In Lisbon and Porto, traffic dropped sharply but briefly, then recovered slightly before declining gradually over time. The most severe immediate impacts occurred in Aveiro, Beja, Bragança, Castelo Branco, Évora, Faro, Guarda, Portalegre, Santarém, Viana do Castelo, Vila Real, and Viseu, where traffic stabilized at very low levels shortly after the outage began. Braga and Setúbal saw a more gradual decline.

Quality and Routing Degradation in Portugal

The power outage degraded network quality across Portugal. Median download speeds fell from approximately 40 Mbps before the outage to as low as 15 Mbps within hours. Median latency correspondingly increased from around 20 ms to nearly 50 ms, consistent with congestion on remaining available links.

Routing infrastructure was also affected. Announced IPv4 address space (measured in /24 blocks) dropped by approximately 300 networks—about 1.2% of the total—while IPv6 /48 announcements declined from 17,928,551 to 16,355,607, a reduction of roughly 9%. Notably, address space began dropping further after 16:00 UTC, suggesting backup power exhaustion at network infrastructure sites.

Spanish Connectivity Takes a Hit

Across Spain, Internet traffic immediately dropped by about 60% compared with the prior week, falling to approximately 80% below baseline within five hours. DNS resolver request traffic declined by 54% initially, but stabilized more quickly than Portugal’s.

Spanish networks, including Digi Spain Telecom (AS57269) and other top providers, saw traffic fall rapidly once power was lost. Most providers experienced gradual declines over several hours, while Digi Spain Telecom's traffic stabilized quickly at the lower level. Overall, traffic from major providers fell between 75% and 93% compared to normal volumes.

Regional differences in Spain showed quick drops and stabilization in most affected areas. Some regions—including Navarre, La Rioja, Cantabria, and Basque Country—exhibited partial traffic recovery, consistent with grid operator Red Eléctrica's update stating that electricity had been restored in parts of those regions along with Catalonia, Aragon, Galicia, Asturias, and others.

Quality and Routing Issues in Spain

Spanish network quality similarly declined. Median download speeds fell from around 35 Mbps to 19 Mbps, though not in a steady decline—speeds fell, recovered, and fell again before dropping overall. Median latency rose from about 22 ms to as high as 40 ms, again pointing to congested remaining infrastructure.

Routing visibility in Spain also suffered. By 14:30 UTC, announced IPv4 /24 blocks had fallen by roughly 2.4%, and IPv6 /48 announcements dropped by over 8%, with both continuing their decline in subsequent hours.

Wider European Effects

While France and Andorra reported electrical disruptions, national traffic patterns showed no clear damage. Regional analysis in some French areas indicated slight declines concurrent with the power outage, but drops were nominal compared to Iberian levels, and traffic returned to expected norms within 90 minutes. No regional effects were evident in Andorra.

More notable was the impact on Morocco’s Orange Maroc network. The provider reported Internet disruptions following the Spanish-Portuguese outage, and traffic data indicates a sharp fall around 12:00 UTC—roughly 90 minutes after the initial power loss—with total outage beginning by 15:00 UTC.

Power restoration was in progress in Spain when analysis was conducted, with full recovery of Internet services expected to follow at the pace of grid restoration. Monitoring traffic, routing, and network quality metrics across the region remains essential to track the ongoing recovery and sequence of events.