Cases2 cases

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1. 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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2. IL-0341 Traffic between Cloudflare and AWS us-east-1 had high latency, packet loss and origin failures for almost four hours

   Cloudflare2025

   Symptoms

   From 16:27 UTC on 21 August 2025, users connecting to Cloudflare from servers in AWS us-east-1, or receiving connections from Cloudflare there, saw high latency, packet loss and failures to reach origins. Cloudflare's network team was alerted to internal congestion in Ashburn (IAD) at 16:44 UTC.

   Packet lossHigh latencyIntermittent timeouts

   Trigger

   At about 16:27 UTC a single customer began sending many requests from AWS us-east-1 to Cloudflare for objects in Cloudflare's cache, doubling the total traffic from Cloudflare to AWS.

   Root cause

   Capacity exhaustion

   Component

   Transit gateway or network interconnectBGP routingCDN and edge network

   Contributing factor

   No headroomHarmful manual actionExcessive blast radius

   Detection

   Cloudflare's network team was alerted to internal congestion in Ashburn (IAD) at 16:44 UTC, and an incident was raised for customer impact at 17:45 UTC.

   Remediation

   • Rate limited the single customer whose traffic caused the surge
   • Took further traffic engineering actions that fully resolved the congestion
   • Asked AWS to revert its BGP prefix withdrawals, which AWS finished at 20:07 UTC

   Action items

   • Build a mechanism to deprioritise a customer's traffic when it congests the network enough to affect others
   • Speed up the Data Center Interconnect upgrades to add network capacity
   • Work with AWS so the two companies' BGP traffic engineering actions do not conflict
   • Build a traffic management system that gives each customer a network resource budget and automates the manual actions used here

   Lessons

   Cloudflare concludes that it must isolate customers better so that no single customer can take over shared network resources and degrade the platform for others, and that its network needs enough capacity to meet demand. It describes the outage as the result of insufficient network congestion management during an unusual high-traffic event.

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