Incident Library
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Cases3 cases

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  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.

    View case
  2. 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
    View case
  3. IL-0539 KT's internet service failed nationwide for about 89 minutes as wrong routes spread from one router in Busan
    KT2021
    Symptoms

    On 25 October 2021 from about 11:16, traffic to the DNS servers in KT's network rose sharply, and then KT's internet service failed across the whole country. KT recognised the internet outage at 11:20, and the outage lasted about 89 minutes until KT finished recovery at about 12:45.

    Network unreachableService outage
    Trigger

    During the replacement of an enterprise network router at KT's Busan office, worked on remotely from the Busan communication center, a worker entered a routing configuration script that lacked the 'exit' command that should have ended the IS-IS part of the configuration.

    Root cause
    Configuration change
    Component
    Interior routing (IGP)BGP routing
    Contributing factor
    Missed in reviewNo configuration testsChange during peak hoursExcessive blast radius
    Detection

    KT recognised the internet outage at 11:20, four minutes after DNS traffic began to surge at 11:16. The Ministry of Science and ICT saw the traffic increase in its own monitoring, and KT reported the outage to the ministry at 11:40.

    Remediation
    • Isolated the router where the faulty routing configuration was entered
    • Logged in to each regional router, deleted the faulty processes and restarted them
    Action items
    • Check the network management of major carriers, including their work procedures and the systems that stop technical errors from spreading
    • Consider having major carriers introduce simulation systems that diagnose errors from network work in advance
    • Have the NMS center and network operations center of each major carrier check technically that approved work plans are followed
    • Strengthen safeguards in routing work, such as limiting the number of route entries updated at once below a set level
    • Strengthen the monitoring of carriers' outages and develop technology, including AI-based preventive diagnosis, for network stability and resilience
    • Prepare structural measures for a stable network architecture and network survivability
    • Let carriers notify users of outages through SNS, text messages and other means, not only the website
    Lessons

    The investigation named management problems and technical problems. On the management side, work approved for the night was done during the day, partner company workers did the routing work without a work manager, and the work was done with the network still connected. On the technical side, the two pre-verification steps were people reading the script and missed the missing 'exit', there was no virtual testbed for trying the work on a disconnected network, and nothing stopped an error in one region from spreading to the whole country.

    View case
Check your cluster for this

These 3 cases involve BGP routing and Backbone network (WAN). kubegap audits a Kubernetes cluster for gaps like these, read-only, from Claude Code or Codex; its checks cite public reports like the ones in this library.

Open kubegap

By root cause1

Configuration change3 cases

Component
BGP routing3Backbone network (WAN)2Interior routing (IGP)2
Contributing factor
No configuration tests3Excessive blast radius2Unverified assumption1Change during peak hours1Harmful manual action1Missed in review1
Organisation
Cloudflare1KT1Microsoft Azure1
  1. IL-0394 A Cloudflare router in Miami leaked IPv6 BGP routes to peers and providers for 25 minutes, congesting the backbone
    Cloudflare2026
  2. IL-0225 An IGP purge command made every Microsoft WAN router recompute routes, causing global latency, timeouts and packet loss
    Microsoft Azure2023
  3. IL-0539 KT's internet service failed nationwide for about 89 minutes as wrong routes spread from one router in Busan
    KT2021