Summary of Impact: Between 07:05 UTC and 09:45 UTC on 25 January 2023, customers experienced issues with networking connectivity, manifesting as network latency and/or timeouts when attempting to connect to Azure resources in Public Azure regions, as well as other Microsoft services including Microsoft 365 and PowerBI.

Preliminary Root Cause: We determined that a change made to the Microsoft Wide Area Network (WAN) impacted connectivity between clients on the internet to Azure, connectivity between services within regions, as well as ExpressRoute connections. 

Mitigation: We identified a recent change to WAN as the underlying cause and have rolled back this change. Networking telemetry shows recovery from 09:00 UTC onwards across all regions and services, with the final networking equipment recovering at 09:35 UTC. Most impacted Microsoft services automatically recovered once network connectivity was restored, and we worked to recover the remaining impacted services.

Next Steps: We will follow up in 3 days with a preliminary Post Incident Review (PIR), which will cover the initial root cause and repair items. We'll follow that up 14 days later with a final PIR where we will share a deep dive into the incident.