Reference Guide

Bidirectional Forwarding Detection | 171
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
• Configuring BFD for Static Routes
• Configuring BFD for OSPF
• Configuring BFD for IS-IS
• Configuring BFD for VRRP
• Configuring BFD for VLANs
• Configuring BFD for Port-Channels
• Configuring Protocol Liveness
• Troubleshooting BFD
Configuring BFD for Physical Ports
BFD on physical ports is useful when no routing protocol is enabled. Without BFD, if the remote system
fails, the local system does not remove the connected route until the first failed attempt to send a packet.
When BFD is enabled, the local system removes the route as soon as it stops receiving periodic control
packets from the remote system.
Configuring BFD for a physical port is a two-step process:
1. Enable BFD globally. Refer to Enabling BFD globally.
2. Establish a session with a next-hop neighbor. Refer to Establishing a session on physical ports.
Related configuration tasks
• Changing physical port session parameters.
• Disabling and re-enabling BFD.