May 27 2025 At 7AM (UTC) on Wednesday May 20th 2025 a BGP message was propagated that triggered surprising (to many) behaviours with two major BGP implementations that are often used for carrying internet traffic. This caused a large number of “internet facing” BGP sessions to automatically shut down, causing at the very least some routing instability, and at worst brief loss of connectivity for some networks. What was the message? Using the sessions that people feed to bgp.tools, we can see her...