Huawei NetEngine80E Configuration Manual - Reliability page 332

HUAWEI NetEngine80E/40E Router
Configuration Guide - Reliability
Figure 5-1 Networking diagram for the one-arm Echo function
BFD-capable
On the network shown in
session with the one-arm Echo function is configured on Router A, detecting the single-hop link
between Router A and Router B. After receiving a BFD Echo packet sent by Router A, Router
B loops back the packet at the IP layer, rapidly detecting the connectivity of the direct link
between Router A and Router B.
Association Between the BFD Status and the Interface Status
If a transmission device exists on a direct link, BFD detects a link fault faster than a fault detection
mechanism provided by a link protocol on an interface. The link protocol status of the trunk
interface or the VLAN interface depends on the link protocol status of member interfaces.
To help BFD more rapidly notify an application of detection results, a BFD status attribute is
added to the interface management module on every interface. This attribute indicates the status
of the BFD session that is bound to the interface (on a sub-interface, this attribute indicates the
status of the BFD session that is bound to the main interface). The system obtains the interface
status based on the link status, protocol status, and BFD status on the interface, and then notifies
the application of the result.
Association between the BFD status and the interface status means that if the BFD session status
changes, the BFD status on the interface in the IFNET module is modified. This function is
applicable only to a single-hop BFD session that is bound to the outgoing interface and uses the
default multicast address. Association is classified into the following modes:
l
Issue 02 (2014-09-30)
RouterA
Figure
Association between BFD status and status of an interface to which BFD is bound
– If a BFD session goes Down, the BFD status on the interface to which the BFD session
is bound goes Down. This status change is reported to an application on the interface.
If the BFD session on a trunk member interface or a VLAN member interface goes
Down, the link protocol status on the trunk or VLAN member interface also changes.
This accelerates the change in the link protocol status and the route convergence.
NOTE
To use single-hop BFD sessions with the default multicast IP address configured as a peer IP
address to monitor the link between trunk member interfaces, you must configure both the
process-interface-status and process-pst commands for BFD sessions on all trunk member
interfaces. This configuration enables a rapid association between the BFD status and trunk
member interfaces' status to reduce packet loss caused by member interface faults.
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5-1, Router A supports BFD but Router B does not. A BFD
5 BFD Configuration
RouterB
BFD-incapable
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