Microsoft has explained what caused the Azure outage last week

Even the biggest corporations and cloud operators have outages. Microsoft says an update on a public-facing router was the reason behind a muti-hour outage that impacted the Microsoft Wide Area Network last Wednesday.  The outage made parts of Azure, Microsoft 365, and Power Platform inaccessible last week.

Prior to the outage, Microsoft did warn customers of an impending update that might cause latency or timeouts around 07:05 UTC on Wednesday.  As workers in Europe started the day it became clear the outage was more than just some packet loss and latency.  The issue began impacting connections inside Microsoft Wan including those between data centers and services including ExpressRoute, Microsoft’s private network which impacted the ability to transfer data between data centers.

Microsoft says in its preliminary incident review that most services were back up and running by 9:00 UTC but not fully recovered under 12:43 UTC on Wednesday, January 25th.  The outage did also impact the Azure Government cloud according to Microsoft.  Microsoft says that it has now blocked highly impactful commands from getting executed on the devices to prevent this in the future and all commands must follow safe change guidelines.  Microsoft plans to publish a full report in a couple of weeks.