RFC 6608BGP FSM Error Subcode May 2012Table of Contents1. Introduction ...22. Requirements Language ...23. Definition of Finite State Machine Error Subcodes ...24. Usage of FSM Error Subcodes ...25. Security Considerations ...
https://notes.networklessons.com/bgp-finite-state-machine-fsm https://www.ciscopress.com/articles/article.asp?p=2756480&seqNum=4 This last one is the most detailed. I assume it is most useful when troubleshooting a complex issue, rather than as a learning aid: https://nwktimes.blogspot....