Bidirectional Forwarding Detection (BFD) | 169Related configuration tasks• Establishing sessions with OSPF neighbors.Establishing sessions with VLAN neighborsTo establish a session, BFD must be enabled at interface level on both ends of the link, as shown in theillustration below. The session parameters do not need to match.Disabling BFD for VLANsIf BFD is disabled on an interface, sessions on the interface are torn down. A final Admin Down controlpacket is sent to all neighbors, and sessions on the remote system change to the Down state (Message 3).To disable BFD on a VLAN interface:Configuring BFD for Port-ChannelsConfiguring BFD for port-channels is supported on platforms: c eBFD on port-channels is analogous to BFD on physical ports. If no routing protocol is enabled, and aremote system fails, the local system does not remove the connected route until the first failed attempt tosend a packet. If BFD is enabled, the local system removes the route when it stops receiving periodiccontrol packets from the remote system.There is one BFD Agent for VLANs and port-channels, which resides on RP2 as opposed to the otheragents which are on the line card. Therefore, the 100 total possible sessions that this agent can maintain isshared for VLANs and port-channels.Step Task Command Syntax Command Mode1 Disable all sessions on a VLAN interface. no bfd enable INTERFACE VLANfnC0043mpFTOS(config-if-gi-4/25)# switchportFTOS(config-if-gi-4/25)# no shutdownFTOS(config-if-gi-4/25)# interface vlan 200FTOS(config-if-vl-200)# ip address 2.2.3.1/24FTOS(config-if-vl-200)# untagged gigabitethernet 4/25FTOS(config-if-vl-200)# no shutdownFTOS(config-if-vl-200)# bfd neighbor 2.2.3.24/25 2/3VLAN 200FTOS(config-if-gi-2/3)# switchportFTOS(config-if-gi-2/3)# no shutdownFTOS(config-if-gi-2/3)# interface vlan 200FTOS(config-if-vl-200)# ip address 2.2.3.2/24FTOS(config-if-vl-200)# untagged gigabitethernet 2/3FTOS(config-if-vl-200)# no shutdownFTOS(config-if-vl-200)# bfd neighbor 2.2.3.2R1 R2
