Huawei NetEngine80E Configuration Manual - Reliability page 330

HUAWEI NetEngine80E/40E Router
Configuration Guide - Reliability
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Discriminators of a dynamic BFD session triggered by a protocol are created as follows:
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The following conditions must be satisfied to allow two ends of a BFD session to create
discriminators in different modes:
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At present, one BFD session working as both a dynamic BFD session and a static BFD session
with automatically negotiated discriminators is supported by BFD for OSPF, BFD for IS-IS,
BFD for BGP, BFD for PIM, and BFD for RSVP-TE.
BFD Modes
The NE80E/40E supports the asynchronous mode.
Asynchronous mode:
Each system sends BFD Control packets at a negotiated interval. If a system does not receive
BFD Control packets from its peer within the detection time, it sets the session to Down.
Single-hop BFD and Multi-hop BFD
The NE80E/40E supports single-hop BFD and multi-hop BFD, both of which check the
reachability of IP routes. This section describes single-hop BFD.
The NE80E/40E supports single-hop BFD for the following types of links:
Issue 02 (2014-09-30)
Static BFD sessions with manually specified discriminators
Static BFD sessions with automatically negotiated discriminators
Dynamic BFD sessions triggered by a protocol
Dynamically allocated local discriminators
Self-learning remote discriminators
NOTE
OSPF, BGP, IS-IS, MPLS, MPLS LDP, RSVP-TE, PWE3, and PIM dynamically trigger the establishment
of BFD sessions on the NE80E/40E.
If a static BFD session is established by manually specifying the discriminators on one end,
the static BFD session on the other end must also be established by manually specifying
discriminators.
If a static BFD session is established by automatically negotiating the discriminators on
one end, the static BFD session on the other end is established by automatically negotiating
discriminators or a dynamic BFD session is established.
If both a static BFD session with automatically negotiated discriminators and a dynamic
BFD session are established on one end, the following principles are applicable:
– If these two sessions share the same configurations (the source address, destination
address, outgoing interface, and VPN index), one BFD session works as both the
dynamic BFD session and the static BFD session with automatically negotiated
discriminators.
– If the dynamic BFD session named DYN_local-discriminator is configured prior to the
static BFD session, the static BFD session's name replaces the dynamic BFD session's
name.
– A shared session uses the minimum values of these two sessions.
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