Bidirectional Forwarding Detection | 175Figure 9-3. BFD State MachineImportant Points to Remember• BFD for line card ports is hitless, but is not hitless for VLANs since they are instantiated on the RPM.• BFD is supported on C-Series and E-Series only.• 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, ISIS (E-Series only), and VRRP protocols as BFD clients.Configuring Bidirectional Forwarding DetectionThe remainder of this chapter is divided into the following sections:• Configuring BFD for Physical Ports on page 176• Configuring BFD for Static Routes on page 180• Configuring BFD for OSPF on page 182• Configuring BFD for BGP on page 185• Configuring BFD for IS-IS on page 193• Configuring BFD for VRRP on page 195• Configuring BFD for VLANs on page 198• Configuring BFD for Port-Channels on page 201• Configuring Protocol Liveness on page 203• Troubleshooting BFD on page 203DownInit UpUp, Admin Down, TimerInitDownAdmin Down,TimerAdmin Down,Down,TimerDownInit, UpUp, Initthe packet receivedcurrent session state
