Bidirectional Forwarding Detection (BFD) | 129Figure 7-3. BFD State Machineo to Remember• BFD for line card ports is hitless, but is not hitless for VLANs since they are instantiated on the RPM.• FTOS supports a maximum of 100 sessions per BFD agent. Each linecard processor has a BFD Agent,so the limit translates to 100 BFD sessions per linecard (plus, on the E-Series, 100 BFD sessions onRP2, which handles LAG and VLANs).• BFD must be enabled on both ends of a link.• Demand mode, authentication, and the Echo function are not supported.• BFD is not supported on multi-hop and virtual links.• Protocol Liveness is supported for routing protocols only.• FTOS supports only OSPF, IS-IS, (E-Series, Z-Series and only), BGP ( only), andVRRP (not on ) protocols as BFD clients.Configuring Bidirectional Forwarding DetectionThe remainder of this chapter is divided into the following sections:• Configuring BFD for Physical Ports• Configuring BFD for Static Routes• Configuring BFD for OSPF• Configuring BFD for IS-IS• Configuring BFD for BGP• Configuring BFD for VRRP• Configuring BFD for VLANs• Configuring BFD for Port-Channels• Configuring Protocol LivenessDownInit UpUp, Admin Down, TimerInitDownAdmin Down,TimerAdmin Down,Down,TimerDownInit, UpUp, Initthe packet receivedcurrent session state
