Figure 9-3. BFD State Machine
current session state
the packet received
Down
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
Up, Admin Down, Timer
Down
Down
Admin Down,
Admin Down,
Timer
Init
Init, Up
Init
Down,
Timer
Up, Init
Up
Bidirectional Forwarding Detection | 175