Cases6 cases

1 to 5 of 6

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.

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2. IL-0349 IONOS Private Cloud in Berlin lost management access, storage and VM internet routing after a VLAN change

   IONOS Cloud2026

   Symptoms

   On 15 January 2026, network services for VMware-based Private Clouds in IONOS Cloud's Berlin location stopped working: customers lost management VPN access and traffic to and from their virtual machines. Inside IONOS, several management interfaces in the Berlin region could no longer be reached.

   Network unreachableStorage disconnected or stale mounts

   Trigger

   During a planned maintenance window to add a new VLAN to the management devices, a human error in the command replaced the existing VLANs on the trunk between the core and management devices instead of adding to them, so only the new VLAN stayed active.

   Root cause

   Operator error

   Component

   Network switchTransit gateway or network interconnect

   Contributing factor

   Excessive blast radiusNo safeguard on destructive change

   Remediation

   • Restarted the affected storage services in the final stage of recovery, which caused a brief second outage

   Action items

   • Audit the management device architecture to segment it better (target Q3 2026)
   • Evaluate and implement ways to prevent unintended VLAN changes, such as improved configuration safeguards or automation scripts (target Q1 2026)

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3. 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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4. IL-0562 Most Linodes in Linode's Dallas data center had intermittent latency and reachability loss from broadcast storms

   Linode2022

   Symptoms

   At about 00:05 UTC, Linode's monitoring systems alerted on reachability problems in the Dallas data center. About 80-90% of the Linodes there had intermittent latency and lost reachability from time to time.

   Intermittent connection failuresHigh latencyIntermittent timeouts

   Root cause

   DNS or network fault

   Component

   Network switch

   Contributing factor

   –

   Detection

   Monitoring systems alerted on reachability problems in the Dallas data center at about 00:05 UTC, and an incident was raised at 00:10.

   Remediation

   • Deployed a filter to the fleet that stemmed the broadcasts, so hosts regained CPU and answered ARP requests
   • Tested the temporary filter further and made it permanent

   Action items

   • Find the root cause of the broadcast storms, taking the other recent Dallas incidents into account
   • Put processes in place to keep the infrastructure stable while upgrades are applied to the active network

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5. 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

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