Dell EMC Networking OS Configuration Guide for the S5048F–ON System 9.14.2.4

Active

The active system initiates the BFD session. Both systems can be active for the same session.

Passive

The passive system does not initiate a session. It only responds to a request for session initialization from the active system.

A BFD session has two modes:

Asynchronous mode

In Asynchronous mode, both systems send periodic control messages at an agreed upon interval to indicate that their session status is Up.’

Demand mode

If one system requests Demand mode, the other system stops sending periodic control packets; it only sends a response to status inquiries from the Demand mode initiator. Either system (but not both) can request Demand mode at any time.

A session can have four states: Administratively Down, Down, Init, and Up.

State

Description

Administratively Down

The local system does not participate in a particular session.

Down

The remote system is not sending control packets or at least not within the detection time for a particular session.

Init

The local system is communicating.

Up

Both systems are exchanging control packets.

The session is declared down if:

• A control packet is not received within the detection time.
• Sufficient echo packets are lost.
• Demand mode is active and a control packet is not received in response to a poll packet.