h3cBfdSessState
1.3.6.1.4.1.43.45.1.10.2.72.1.3.1.12
The state of the running BFD session.
There are three states through which a session normally
proceeds, two for establishing a session (Init and Up)
and one for tearing down a session (Down.) This allows
a three-way handshake for both session establishment and
session teardown (assuring that both systems are aware of
all session state changes.) A fourth state (AdminDown)
exists so that a session can be administratively put down
indefinitely.
The Down state means that the session is down (or has just been
created.) A session remains in Down state until the remote
system indicates that it agrees that the session is down by
sending a BFD Control packet with the State field set to
anything other than Up. If that packet signals Down state,
the session advances to Init state; if that packet signals
Init state, the session advances to Up state.
Init state means that the remote system is 0communicating,
and the local system desires to bring the session up, but
the remote system does not yet realize it. A session will
remain in Init state until either a BFD Control Packet is
received that is signaling Init or Up state (in which case
the session advances to Up state) or until the detection time
expires, meaning that communication with the remote system
has been lost (in which case the session advances to Down
state.)
Up state means that the BFD session has successfully been
established, and implies that connectivity between the systems
is working. The session will remain in the Up state until either
connectivity fails, or the session is taken down administratively.
If either the remote system signals Down state, or the detection
time expires, the session advances to Down state.
AdminDown state means that the session is being held
administratively down. This causes the remote system to enter
Down state, and remain there until the local system exits
AdminDown state.