Call2Teams - West US region intermittent networking outage

On July 23, 2026, a routine device maintenance required isolating specific network paths. Our maintenance process converts these requests into system-readable requests and verifies that at least one of the two redundant paths remains healthy. Before maintenance begins, these requests undergo safety checks to confirm the work will be impact-less. In this case, a bug in the request conversion system incorrectly marked additional devices as a part of the maintenance event and caused a set of IP routes to be removed from more devices than intended. The routes were removed between our datacenter and wide-area network, impacting traffic entering or exiting the region.

At 14:44 UTC, customers started experiencing impact and the engineering team was engaged immediately. The issue initially presented as large-scale route churn in our Wide-Area Network (WAN). It was later found that route removal was from a datacenter in the West US region. Once confirmed, engineers began roll back at 17:45 UTC. By 18:26 UTC, the network was restored and healthy, and all impacted services had fully recovered by 19:41 UTC.

Microsoft: We identified a recent change that was strongly correlated with the onset of impact. We have completed the rollback of this change and telemetry across services are continuing to show signs of recovery. Customer should be observing recovery at this time.

We are closely monitoring service health and downstream recovery and will provide additional updates as we validate restoration

This message was last updated at 18:47 UTC on 23 July 2026

We are investigating a networking issue affecting connectivity to services in the West US region. Impacted customers may experience intermittent connectivity failures, increased latency, or difficulty accessing services. Customers with traffic traversing the West US region may also experience downstream impact.