Cloudflare outage on June 21, 2022

This post details a significant outage on June 21, 2022, caused by a misconfiguration during a BGP policy change in Cloudflare's newly architected Multi-Colo PoP (MCP) data centers. The change inadvertently withdrew critical site-local prefixes, leading to a loss of connectivity to 19 major data centers and impacting 50% of global traffic. The post provides a detailed timeline, technical description of the error (re-ordering of BGP policy terms causing an explicit reject), and outlines remediation steps focusing on process improvements, architectural redesigns, and enhanced automation for staggered rollouts and automated rollback.