IETF RFC 9355 PDF

This document specifies the extensions to OSPF that enable an OSPF router to signal the requirement for a Bidirectional Forwarding Detection (BFD) session prior to adjacency formation. Link-Local Signaling (LLS) is used to advertise the requirement for strict-mode BFD session establishment for an OSPF adjacency. If both OSPF neighbors advertise BFD strict-mode, adjacency formation will be blocked until a BFD session has been successfully established.

This document updates RFC 2328 by augmenting the OSPF neighbor state machine with a check for BFD session up before progression from Init to 2-Way state when operating in OSPF BFD strict-mode.