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Cases2 cases

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  1. IL-0568 A layer 2 loop after an access switch change broke network traffic across a whole DeNA site, with mass MACFLAP logs
    DeNA2026
    Symptoms

    At about 20:00 on a weekday, one of DeNA's largest sites reported that terminals of a customer-facing system could not communicate and business was suffering. The network group's monitoring had raised no alert.

    Intermittent connection failuresHigh latency
    Trigger

    During a routine change on 15 Cisco Catalyst 2960L access switches at the site, which tidied descriptions, added VLAN definitions and added allowed VLANs on trunk ports, `no switchport trunk allowed vlan` was applied to GigabitEthernet0/15 of switch SW3, only one of the two physical ports in the LACP bundle between SW3 and SW2.

    Root cause
    Operator error
    Component
    Network switch
    Contributing factor
    Monitoring blind spotNo staged rolloutNo runbookChange during peak hours
    Detection

    The site reported the problem at about 20:00; no monitoring alert fired, because the affected port had no interface monitoring and LACP monitoring had been removed by an earlier monitoring change.

    Remediation
    • Rolled back the switch changes without knowing the cause; service recovered when the interface setting of one switch was restored
    • Found the faulty port and confirmed there was no other impact, completing the first response at about 22:00
    Action items
    • Fix the missing interface and LACP monitoring
    • Require a review for every monitoring change
    • Block merges to the alert rule repository without a reviewer's approval
    • Enable automatic AI review on pull requests
    • Announce every network change in advance, however minor
    • Agree the work date with the site's managers and avoid the site's event days
    • Prepare rollback procedures for high-impact maintenance and for work on several devices at once
    Lessons

    Any change can cause an outage, through a mistake, an unexpected event or a bug, so changes need to be scheduled with a maintenance window agreed in advance. A change on a downstream access switch can affect the whole site. Changing many devices at once made it slow both to find the faulty device and to roll back, and the parts that can be prevented by mechanisms rather than by people's care, such as reviews and monitoring, should be enforced that way.

    View case
  2. IL-0525 OpenStreetMap.org went offline for 7h 27m when its uplink switch lost power during a data-centre power feed maintenance
    OpenStreetMap Foundation2022
    Symptoms

    From 20:18 UTC on 11 June 2022, OpenStreetMap.org was unavailable: all of its services hosted in Amsterdam, including www, the API, the wiki and planet, had no connectivity to the Internet. The outage began 18 minutes into Equinix's planned maintenance of power feed A at the Amsterdam data centre.

    Network unreachableService outage
    Trigger

    Equinix's planned 5-year maintenance of power feed A in Amsterdam, which started at 20:00 UTC on 11 June 2022.

    Root cause
    Hardware failure
    Component
    Network switchData center power and cooling
    Contributing factor
    Single point of failureLimited debug accessMonitoring blind spot
    Remediation
    • Waited for the end of the Equinix power feed A maintenance window instead of failing over to Dublin or moving the uplink; connectivity returned at 03:45 UTC
    Action items
    • Acknowledge ongoing outages faster
    • Add monitoring and alerting of switch PSU and FAN states
    • Replace the Cisco SG550X-48 switches and the Redundant Power System with Juniper EX4300 switches with redundant power supplies
    • Install out-of-band access equipment with dual power feeds in Amsterdam
    • Install redundant uplinks
    • Make site failover easier, less manual and lower risk
    • Introduce an on-call pager system for the operations SRE
    • Expand the SRE team
    • Continue and formalise fail-over tests for power, network, upstream link and service outages
    View case
Check your cluster for this

These 2 cases involve Network switch and Data center power and cooling. 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 cause2

Operator error1 case

Component
Network switch
Contributing factor
Change during peak hoursMonitoring blind spotNo runbookNo staged rollout
Organisation
DeNA
  1. IL-0568 A layer 2 loop after an access switch change broke network traffic across a whole DeNA site, with mass MACFLAP logs
    DeNA2026

Hardware failure1 case

Component
Data center power and coolingNetwork switch
Contributing factor
Limited debug accessMonitoring blind spotSingle point of failure
Organisation
OpenStreetMap Foundation
  1. IL-0525 OpenStreetMap.org went offline for 7h 27m when its uplink switch lost power during a data-centre power feed maintenance
    OpenStreetMap Foundation2022