This article explains BGP zombies, which are routing entries that linger in the Internet's routing tables despite being withdrawn. It describes how path hunting can lead to these zombies forming and discusses the operational challenges they create for network operators. The piece also illustrates scenarios where BGP zombies can occur, both between networks and within a single network.

A BGP message propagated on May 20th, 2025, caused session resets in JunOS and Arista EOS, leading to significant internet routing instability and brief connectivity loss for numerous networks. The incident stems from a corrupt BGP Prefix-SID Attribute that unexpectedly leaked into the global routing table, impacting various autonomous systems and illustrating the vulnerabilities within BGP error handling. The widespread disruption highlights the potential real-world consequences of such network bugs as reliance on IP-based services increases.