Cases7 cases

1 to 5 of 7

1. IL-0394 A Cloudflare router in Miami leaked IPv6 BGP routes to peers and providers for 25 minutes, congesting the backbone

   Cloudflare2026

   Symptoms

   On 22 January 2026 from 20:25 UTC, a Cloudflare edge router in Miami sent unintended BGP advertisements of IPv6 prefixes to its transit providers and peers. External networks' traffic was funnelled into the Miami data center, the backbone between Miami and Atlanta became congested, and some Cloudflare customer traffic saw elevated loss and higher latency.

   Packet lossHigh latency

   Trigger

   At 20:25 UTC Cloudflare's policy automation pushed a change, merged at 19:52 UTC, that removed the BGP announcements from Miami for a data center in Bogotá, Colombia, by deleting the prefix-list 6-BOG04-SITE-LOCAL from several export policy terms.

   Root cause

   Configuration change

   Component

   BGP routingBackbone network (WAN)

   Contributing factor

   No configuration tests

   Detection

   The network team began investigating unintended route advertisements from Miami at 20:40 UTC, and an incident was raised at 20:44 UTC.

   Remediation

   • A network operator reverted the bad configuration change on the Miami router by hand
   • Paused the automation for the router so it could not run again
   • Reverted the triggering change in the network automation code repository
   • Unpaused the automation on the Miami router after confirming it ran without the routing policy bug

   Action items

   • Patch the failure in the routing policy automation that caused the leak
   • Add BGP community-based safeguards that reject routes received from providers and peers on external export policies
   • Add automatic routing policy evaluation to the CI/CD pipelines that looks for empty or erroneous policy terms
   • Detect problems in network configurations and the effects of automated changes earlier
   • Validate routing equipment vendors' implementations of RFC9234 before rolling out BGP roles and the Only-to-Customer Attribute
   • Encourage long-term adoption of RPKI Autonomous System Provider Authorization (ASPA)

   Lessons

   Removing only the prefix lists from export policy terms left terms that were too permissive, because a match on route-type internal accepts IBGP routes as well. Cloudflare states that route leaks are easy to cause by accident and that RFC9234 is the only way, independent of routing policy, to prevent route leaks caused at the local AS.

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2. IL-0564 Linode's Miami, Milan and Sao Paulo data centers had packet loss as traffic moved onto congested alternate paths

   Linode2025

   Symptoms

   Customers using Linode's US-MIA (Miami) and IT-MIL (Milan) data centers saw packet loss and brief performance problems on 14 September 2025 from 17:42 to 18:43 UTC. BR-GRU (Sao Paulo) had the same packet loss on 15 September 2025 from 01:44 to 04:22 UTC.

   Packet loss

   Trigger

   A gradual increase in prefixes pushed the routing between the core router and the edge router past the maximum number of permitted prefixes.

   Root cause

   Capacity exhaustion

   Component

   BGP routingBackbone network (WAN)

   Contributing factor

   –

   Remediation

   • Raised the prefix limit on all the data center routers

   Action items

   • Raise the thresholds of the sessions between Akamai's backbone and the data center ECOR routers
   • Improve the existing alerting and check its severity before limits are reached, with escalation to the right team for immediate action

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3. IL-0341 Traffic between Cloudflare and AWS us-east-1 had high latency, packet loss and origin failures for almost four hours

   Cloudflare2025

   Symptoms

   From 16:27 UTC on 21 August 2025, users connecting to Cloudflare from servers in AWS us-east-1, or receiving connections from Cloudflare there, saw high latency, packet loss and failures to reach origins. Cloudflare's network team was alerted to internal congestion in Ashburn (IAD) at 16:44 UTC.

   Packet lossHigh latencyIntermittent timeouts

   Trigger

   At about 16:27 UTC a single customer began sending many requests from AWS us-east-1 to Cloudflare for objects in Cloudflare's cache, doubling the total traffic from Cloudflare to AWS.

   Root cause

   Capacity exhaustion

   Component

   Transit gateway or network interconnectBGP routingCDN and edge network

   Contributing factor

   No headroomHarmful manual actionExcessive blast radius

   Detection

   Cloudflare's network team was alerted to internal congestion in Ashburn (IAD) at 16:44 UTC, and an incident was raised for customer impact at 17:45 UTC.

   Remediation

   • Rate limited the single customer whose traffic caused the surge
   • Took further traffic engineering actions that fully resolved the congestion
   • Asked AWS to revert its BGP prefix withdrawals, which AWS finished at 20:07 UTC

   Action items

   • Build a mechanism to deprioritise a customer's traffic when it congests the network enough to affect others
   • Speed up the Data Center Interconnect upgrades to add network capacity
   • Work with AWS so the two companies' BGP traffic engineering actions do not conflict
   • Build a traffic management system that gives each customer a network resource budget and automates the manual actions used here

   Lessons

   Cloudflare concludes that it must isolate customers better so that no single customer can take over shared network resources and degrade the platform for others, and that its network needs enough capacity to meet demand. It describes the outage as the result of insufficient network congestion management during an unusual high-traffic event.

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4. IL-0347 About 25% of Scaleway FR-PAR-1 hypervisors lost VPC connectivity when both VPC BGP route reflectors got stuck

   Scaleway2024

   Symptoms

   On 18 October 2024, from 7:50 to 8:01 UTC, about 25% of the hypervisors in Scaleway's FR-PAR-1 availability zone lost VPC connectivity with the rest of the region, and products that use VPC failed with them. Public internet connectivity and Elastic Metal VPC connectivity were not affected.

   Network unreachablePacket lossNode NotReady

   Trigger

   At 6:20 UTC a Top of Rack switch in FR-PAR-1 had a software crash. One of the two BGP route reflectors for VPC ran on a hypervisor in that rack and was left in an abnormal state.

   Root cause

   Software defect

   Component

   Network control plane (SDN)BGP routingNetwork switchDatabaseManaged Kubernetes control plane and provider API

   Contributing factor

   Excessive blast radiusAutomation amplification

   Detection

   Health-check monitoring on both route reflectors detected the anomaly, and the Scaleway Customer Excellence and SRE teams detected the customer impact and opened an incident.

   Remediation

   • Fixed both VPC route reflectors by manual action

   Action items

   • Fixed the autohealing mechanism that had failed to fix route reflectors stuck in a stale state; the fix is https://github.com/FRRouting/frr/pull/17163
   • Run different software versions on the route reflectors so a single bug cannot stop several instances
   • Investigate the software issue that left the route reflectors in a stale state

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5. IL-0225 An IGP purge command made every Microsoft WAN router recompute routes, causing global latency, timeouts and packet loss

   Microsoft Azure2023

   Symptoms

   From 07:08 UTC on 25 January 2023, customers saw long network latency and timeouts when connecting to resources in Azure regions and to other Microsoft services such as Microsoft 365 and Power Platform. Microsoft's monitoring detected DNS and WAN issues from 07:11 UTC.

   High latencyIntermittent timeoutsIntermittent connection failuresPacket lossNetwork unreachable

   Trigger

   A network engineer adding capacity to the global WAN in Madrid ran a step of a recently changed standard operating procedure that purged the IGP database; on the router manufacturer involved, that command runs on all IGP-joined routers instead of only the local one.

   Root cause

   Configuration change

   Component

   Backbone network (WAN)Interior routing (IGP)BGP routing

   Contributing factor

   No configuration testsUnverified assumptionExcessive blast radiusHarmful manual action

   Detection

   Monitoring detected DNS and WAN issues from 07:11 UTC and alerted the on-call engineers within 5 minutes of the command being run. The team reviewed all recent changes and identified the command by 08:20 UTC. The engineer making the change was not informed of the alerts because of the unqualified changes to the SOP.

   Remediation

   • Restarted by hand the paused WAN health and traffic engineering systems, which ended the remaining packet loss

   Action items

   • Audit and block similar widespread-impact commands across all three vendors for all WAN router roles
   • Give on-call engineers real-time visibility of approved and unqualified activity on network devices
   • Run regular mandatory operational training and attestation of following all SOPs
   • Have the Change Advisory Board review all SOPs still pending qualification within 30 days

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