Bfd Echo Function - Huawei AR2200-S Series Configuration Manual

Huawei AR2200-S Series Enterprise Routers
Configuration Guide - Reliability
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BFD Echo Function

Among two directly connected devices, one device supports BFD, whereas the other device does
not support BFD. To rapidly detect forwarding failures between the two devices, the BFD echo
function is configured on the BFD-supporting device. The BFD-supporting device sends an Echo
Request packet to the remote device. The remote device sends the Echo Request packet back
along the same path to detect the connectivity of the forwarding link.
Figure 3-1 Networking diagram for the BFD echo function
BFD-capable
As shown in
BFD echo function is configured on RouterA to detect the connectivity of the single-hop path
between RouterA and RouterB. After RouterB receives a BFD echo packet from RouterA,
RouterB loops back the packet. This function rapidly detects the connectivity of the direct link
between RouterA and RouterB.
Association Between the BFD Session Status and Interface Status
If a transmission device exists on a direct link, BFD detects a link fault faster than a link protocol
on an interface. The link protocol status of a trunk or VLANIF interface depends on the link
protocol status of member interfaces.
To help BFD rapidly report the detection result to the application, a BFD status attribute is added
to the interface management module of each 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
Issue 01 (2012-01-06)
Physical interfaces: Layer 2 and Layer 3 Ethernet interfaces
Logical interfaces: Layer 2 Eth-Trunk interfaces, Layer 3 Eth-Trunk interfaces, and
Ethernet sub-interfaces (including Dot1q sub-interfaces and QinQ sub-interfaces)
NOTE
l Multicast BFD sessions cannot be established on Layer 2 Ethernet interfaces, Layer 2 Eth-Trunk
interfaces, or Layer 3 Eth-Trunk interfaces of AR200 or AR1220 SRUs.
l On Layer 2 Ethernet interfaces, a multicast BFD session must be established on the Layer 2 Ethernet
interface in the default VLAN (VLAN 1).
l When a physical Ethernet interface has multiple sub-interfaces, a BFD session can be established on
the physical Ethernet interface or each sub-interface.
NOTE
The BFD echo function is only applicable to single-hop BFD sessions.
RouterA
Figure 3-1, RouterA supports BFD, whereas RouterB does not support BFD. The
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3 BFD Configuration
RouterB
BFD-incapable
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