Incident Library
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Cases6 cases

5 to 6 of 6

  1. IL-0533 Names in chinacloudapp.cn and chinacloudsites.cn stopped resolving as DNS caches expired, breaking Azure China services
    Microsoft Azure2024
    Symptoms

    From 03:45 CST on 23 April 2024, FQDNs in two system domains of Azure in China, chinacloudapp.cn and chinacloudsites.cn, gradually stopped resolving, and customers in the Azure China regions had trouble connecting to many Azure services and managing resources. Internal monitors alerted engineers to the degradation at 04:37 CST.

    DNS resolution failuresHigh error rateMonitoring outage
    Trigger

    At 03:45 CST a configuration change made through a domain registrar, as a step of a domain decommissioning workflow, updated the nameservers of chinacloudapp.cn and chinacloudsites.cn to a set of inactive servers.

    Root cause
    Configuration change
    Component
    Authoritative DNS servers and records
    Contributing factor
    Unverified assumptionCache-masked failure
    Detection

    Internal monitors alerted engineers to the degradation in the Azure China Cloud at 04:37 CST and created an incident, which the engineering team acknowledged at 04:39 CST.

    Remediation
    • Reverted the two domains to their previous working nameservers
    Action items
    • Suspended further runs of the domain lifecycle process until the management tool covers Azure in China
    • Make the validation process of domain lifecycle management include signals from all cloud regions
    • Add validations that get nameserver information by resolving the zone directly over the Internet
    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
Check your cluster for this

These 6 cases involve Model inference server 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.

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By root cause1

Configuration change6 cases

Component
Model inference server2Backbone network (WAN)1BGP routing1Cloud block storage1Automated capacity manager1CDN and edge network1Database1Data center power and cooling1DDoS protection service1Authoritative DNS servers and records1Database failover manager1Interior routing (IGP)1Model request routing1Network control plane (SDN)1
Contributing factor
Unverified assumption3Excessive blast radius3Monitoring blind spot3No staged rollout2Overlapping failures2Cache-masked failure1Harmful manual action1No configuration tests1No safeguard on destructive change1Unrepresentative staging1Unsafe failure behaviour1
Organisation
Microsoft Azure6
  1. IL-0235 Azure OpenAI GPT-5.2 returned HTTP 400 in seven regions after a configuration update the model engine did not support
    Microsoft Azure2026
  2. IL-0339 Azure Front Door and Azure CDN users saw intermittent connection errors, timeouts and latency spikes for hours
    Microsoft Azure2024
  3. IL-0367 Azure Storage in Central US rejected VM disk I/O, taking down VMs and the SQL Database and Cosmos DB services on them
    Microsoft Azure2024
  4. IL-0407 Azure OpenAI returned 5xx errors in 14 of 28 regions after an automated cleanup deleted its GPU VMs and endpoints
    Microsoft Azure2024
  5. IL-0533 Names in chinacloudapp.cn and chinacloudsites.cn stopped resolving as DNS caches expired, breaking Azure China services
    Microsoft Azure2024
  6. IL-0225 An IGP purge command made every Microsoft WAN router recompute routes, causing global latency, timeouts and packet loss
    Microsoft Azure2023