Graph
Cases3 cases
1 to 3 of 3
IL-0350Hosts in an IONOS TXL cluster lost connectivity when an InfiniBand fabric resweep failed on a full multicast tableIONOS Cloud2026- Symptoms
On 3 March 2026, during a scheduled maintenance to replace a faulty switch in a cluster in IONOS Cloud's TXL data center, monitoring alerts fired and the hosts in that cluster lost network connectivity. Customers saw intermittent network degradation or outages, and the Data Center Designer (DCD) web frontend and the AI Model Hub became unreachable.
- Trigger
During a scheduled maintenance to replace a faulty switch, Topology 2 of 2 in the affected cluster was disabled as planned, and a link flap on a switch in Topology 1 then flooded the InfiniBand control plane with alerts and started a fabric resweep.
- Root cause
- Component
- Contributing factor
- Detection
IONOS began investigating monitoring alerts in TXL; the first status update was posted at 11:36 UTC.
- Remediation
- Switched from the affected control plane to its standby
- Rebooted the locked-up gateways
- Recovered Topology 1 from the scheduled maintenance
- Paused provisioning in the cluster that had a backlog of queued jobs
- Re-enabled provisioning once network connectivity improved and watched job execution
- Re-established connectivity for the systems that support the DCD
- Action items
- Adjusted the control-plane configuration to use less aggressive failover timers and reduced heavy sweep activity, lowering the load on the forwarding table
- Reduced the number of multicast group memberships to relieve the forwarding table
- Set up continuous monitoring of forwarding table use and control-plane memory with alerts before capacity limits are reached
- Move the control plane to dedicated high-performance servers, separate from data-plane traffic
- Audit IPv6 configurations and IPoIB driver settings
- Modernise the interconnect fabric, including switches, gateways and drivers
- Hardened IAM maintenance protocols so that critical identity services keep working when the primary Cloud APIs are temporarily unavailable
- Move IAM to a dedicated platform without a dependency on the standard managed Kubernetes clusters
- Introduce a dedicated provisioning provider for DBaaS and Managed Kubernetes
- Add automated circuit breakers to the provisioning engine against overload and queue buildup from self-healing services
- Improve visibility and control over job execution and prioritisation in the provisioning queue
- Change the provisioning queue architecture to decouple services and reduce spillover
- Lessons
IONOS identified the linking of services through the shared provisioning queue as a key reason the degradation lasted as long as it did. Alongside making each service more robust, it is decoupling the provisioning queue and addressing dependencies between services to reduce the blast radius of future incidents.
IL-0539KT's internet service failed nationwide for about 89 minutes as wrong routes spread from one router in BusanKT2021- 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.
- 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
- Component
- Contributing factor
- 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.
IL-0228IPv4 routing across OVHcloud's global network broke after a router change put the full internet routing table into OSPFOVHcloud2021- Symptoms
At 09:20 CET on 13 October 2021, during a planned change on a router, IPv4 traffic across OVHcloud's whole network stopped being routed, while all IPv6 traffic stayed reachable. The team detected a problem with the router's performance at 09:21 CET and escalated at once.
- Trigger
A planned change to a router in the Vint Hill datacentre in the United States, meant to strengthen anti-DDoS protection, included a command to regulate the redistribution of BGP into OSPF, and the router did not interpret that command correctly.
- Root cause
- Component
- Contributing factor
- Detection
At 09:21 CET the team detected a problem with the router's performance and started the escalation process.
- Remediation
- Disconnected the optical equipment to isolate the router's connectivity
- Powered off the faulty router
- Stabilised connectivity to restore the remaining services
- Action items
- Re-evaluate the change procedure for this type of equipment, which applies the command line natively
- Strengthen the related change process
These 3 cases involve BGP routing and Interior routing (IGP). 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.
By root cause2
Capacity exhaustion1 case
- Component
- Contributing factor
- Organisation
Configuration change2 cases
- Contributing factor