Alcatel-Lucent 6850-48 参考指南
OmniSwitch CLI Reference Guide
September 2009
page 39-1
39 BFD Commands
Bidirectional Forwarding Detection (BFD) is a hello protocol, which can be configured to interact with
routing protocols for the detection of path failures and can reduce the convergence time in a network. BFD
is supported with the BGP, OSPF, VRRP, and Static Routes.
routing protocols for the detection of path failures and can reduce the convergence time in a network. BFD
is supported with the BGP, OSPF, VRRP, and Static Routes.
When BFD is configured and enabled, BFD sessions are created and timers are negotiated between BFD
neighbors. If a system does not receive a BFD control packet within the negotiated time interval, the
neighbor system is considered down. Rapid failure detection notices are then sent to the routing protocol,
which initiates a routing protocol recalculation. This process can reduce the time of convergence in a
network.
neighbors. If a system does not receive a BFD control packet within the negotiated time interval, the
neighbor system is considered down. Rapid failure detection notices are then sent to the routing protocol,
which initiates a routing protocol recalculation. This process can reduce the time of convergence in a
network.
BFD can be operated in three different modes: Asynchronous mode, Demand mode or Echo mode.
In Asynchronous mode, the systems continuously send BFD control packets between each other as part of
a BFD session. If there are no packets received for a minimum time interval negotiated between the
systems, then the neighbor system is considered down.
a BFD session. If there are no packets received for a minimum time interval negotiated between the
systems, then the neighbor system is considered down.
In Demand mode, a poll sequence is initiated for which there is an exchange of BFD control packets. If the
demand mode is active and no control packets are received in response to the poll sequence, the session is
declared down.
demand mode is active and no control packets are received in response to the poll sequence, the session is
declared down.
In Echo mode, a stream of BFD echo packets are transmitted in a forwarding path for which the neighbor-
ing system would loop the packets and send them back. If the number of packets transmitted is not echoed
back, then the system is declared down. Echo mode can be operated along with Asynchronous mode and
Demand mode.
ing system would loop the packets and send them back. If the number of packets transmitted is not echoed
back, then the system is declared down. Echo mode can be operated along with Asynchronous mode and
Demand mode.
MIB information for the BFD commands is as follows:
Filename: ALCATEL-IND1-BFD-MIB
Module: ALCATEL-IND-BFD-MIB
Module: ALCATEL-IND-BFD-MIB