Facebook, Instagram, and WhatsApp were hit by a global outage on Monday beginning at approximately 15:50 UTC and continuing for almost 6 hours. In July, Facebook reported 3.51 billion people are using at least one of its apps every month.
Facebook CTO Mike Schroepfer attributed the outage to networking issues and offered the company's apologies.
In a blog post, Facebook Engineering Group's Santosh Janardhan said the root cause of the outage was a faulty configuration change on the backbone routers that coordinate network traffic between data centers. The disruption cascaded across Facebook's application, including internal tools the company uses to manage its infrastructure.
Cloudflare said the issue appeared more serious than a DNS misconfiguration because it appeared as if Facebook had stopped announcing the BGP routes to their DNS prefixes, making their infrastructure IPs suddenly were unreachable as "if someone had pulled the cables from their data centers all at once and disconnected them from the Internet."
https://engineering.fb.com/2021/10/04/networking-traffic/outage/
https://blog.cloudflare.com/october-2021-facebook-outage/
