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Bidirectional Forwarding Detection | 175
Figure 9-3. BFD State Machine
Important 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 on
RP2, 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 Detection
The 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 203
Down
Init
Up
Up, Admin Down, Timer
Init
Down
Admin Down,
Timer
Admin Down,
Down,
Timer
D
own
Init, Up
Up, I
nit
the packet received
current session state