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Configuration Guide - IP Unicast Routing
CloudEngine 12800 and 12800E V200R002C50

This document describes the configurations of IP Unicast Routing, including IP Routing, Static Route, RIP, RIPng, OSPF, OSPFv3, IPv4 IS-IS, IPv6 IS-IS, BGP, Routing Policy, and PBR.

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Bidirectional Forwarding Detection (BFD) is a mechanism to detect communication faults between forwarding engines.

To be specific, BFD detects connectivity of a data protocol on a path between two systems. The path can be a physical link, a logical link, or a tunnel.

In BFD for OSPF, a BFD session is associated with OSPF. The BFD session can quickly detect a link fault and then notify OSPF of the fault. This speeds up OSPF's response to the change of the network topology.


A link fault or a topology change may cause devices to re-calculate routes. Therefore, the convergence of routing protocols must be as quick as possible to improve the network performance.

Link faults are unavoidable. Therefore, a feasible solution is required to detect faults fast and notify routing protocols of the faults immediately. With BFD being associated with OSPF, once a fault occurs on a link between neighbors, BFD can speed up the OSPF convergence.

Table 5-10 Comparison before and after BFD for OSPF is enabled

Associated with BFD

Link Fault Detection Mechanism

Convergence Speed


An OSPF dead timer expires. The default value of the dead timer is 40s.

At the second level


A BFD session goes Down.

At the millisecond level


Figure 5-2 BFD for OSPF

Figure 5-2 shows the implementation of BFD for OSPF.

  1. OSPF neighbor relationships are established between three routers.

  2. After the status of a neighbor relationship reaches Full, BFD is instructed to establish a BFD session.

  3. The outbound interface from Router A to Router B is GE 2/0/0. When the link fails, BFD immediately detects the fault and then notifies Router A of the fault.

  4. Router A processes the event that a neighbor relationship becomes Down and re-calculates routes. After calculation, the outbound interface becomes GE 1/0/0 on Router C. Traffic from Router A passes through Router C to get to Router B.

Updated: 2019-03-21

Document ID: EDOC1000166601

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