BFD

BFD is used by netverdict as a fast failure signal for routing protocols. It does not try to be a byte-perfect UDP implementation; it provides deterministic session state that OSPF and BGP can depend on.

Support level

Area	Level	Notes
BFD sessions	Supported	Session state is tracked between enabled peers.
OSPF integration	Supported	`ip ospf bfd` and `bfd all-interfaces` can gate adjacency.
BGP integration	Supported	`neighbor ... fall-over bfd` can force a session down.
Timers	Behaviour model	Deterministic event queue, not real-time sleeps.
Echo mode	Not modelled	Control-plane signalling is enough for current labs.

Standards coverage

Standard	Coverage	Notes
RFC 5880	Behaviour model	Session up/down state and detection-multiplier semantics.

Feature matrix

Feature	Status	Notes
Session creation	Supported	Built from protocol/interface configuration.
Administrative down	Supported	Down state propagates to dependent protocols.
Detection multiplier	Partial	Stored and used where exposed.
Per-interface enable	Supported	Used by OSPF.
Per-neighbour enable	Supported	Used by BGP fall-over.

Vendor command matrix

Command	IOS-style	Junos-style	VyOS-style	Notes
`ip ospf bfd`	Supported	n/a	n/a	Interface-level OSPF integration.
`bfd all-interfaces`	Supported	n/a	n/a	OSPF process-wide integration.
`neighbor 10.0.0.2 fall-over bfd`	Supported	Not yet	Partial	BGP integration.
`show bfd neighbors`	Supported	Partial	Partial	Session state view.

Behaviour notes

When BFD transitions down, dependent sessions become unusable in the same deterministic event model. This makes failover labs repeatable.

Examples

Canonical example

configure terminal
router ospf 1
 bfd all-interfaces
router bgp 65001
 neighbor 10.0.12.2 remote-as 65002
 neighbor 10.0.12.2 fall-over bfd
end
show bfd neighbors

Vendor styles

IOS-style

interface GigabitEthernet0/0
 bfd interval 50 min_rx 50 multiplier 3
 ip ospf bfd
router bgp 65001
 neighbor 10.0.12.2 fall-over bfd

Junos-style

set protocols ospf area 0 interface ge-0/0/0.0 bfd-liveness-detection minimum-interval 50
set protocols bgp group EBGP neighbor 10.0.12.2 bfd-liveness-detection minimum-interval 50

VyOS-style

set protocols bgp neighbor 10.0.12.2 bfd
set protocols ospf interface eth0 bfd

Known limits

Asynchronous vs demand mode nuance, echo mode, authentication, and packet-level UDP details are not modelled.