Microsoft fiber foul-up cut off Azure California for almost five hours
Microsoft’s West US Azure region suffered an outage lasting almost five hours after routine network maintenance mistakenly removed IP routes between a datacentre and Microsoft’s wide-area network. The disruption affected 27 Azure services and prevented traffic entering or leaving the Californian region, underlining how maintenance errors can affect supposedly resilient cloud infrastructure.
The incident began at 14:44 UTC on 23 July, when a bug in Microsoft’s maintenance-request conversion system incorrectly included additional devices in the work. Microsoft began rolling back changes at 17:45 UTC; its wide-area network recovered by 18:26, and all affected services were restored by 19:41.
In short
- A maintenance bug disrupted Azure West US for nearly five hours.
- Incorrect route removals affected 27 Azure services.
- Full recovery was completed at 19:41 UTC.
Explained simply
Microsoft Azure is a cloud service that stores data and runs applications for businesses and organisations around the world. Millions of companies depend on Azure to keep their websites, email systems and databases running.
In July, Microsoft's California data centre region went offline for almost five hours after maintenance work went wrong. A software bug caused the system to incorrectly disconnect the data centre from Microsoft's network, stopping all data from moving in or out.
The outage disabled 27 different Azure services and affected countless businesses relying on them. The incident shows how maintenance errors can disrupt cloud infrastructure, even systems designed to be highly resilient.