R3303-HP HSR6800 Routers MPLS Configuration Guide

Configuring BFD for LSPs

You can configure BFD to detect the connectivity of an LSP. After the configuration, a BFD session is

established between the ingress and egress of the LSP. The ingress adds the label for the FEC into a BFD

control packet, forwards the BFD control packet along the LSP to the egress, and determines the status of

the LSP according to the reply received. Upon detecting an LSP failure, BFD triggers a traffic switchover.

A BFD session for LSP connectivity detection can be static or dynamic.

• Static—If you specify the local and remote discriminator values by using the discriminator keyword

when configuring the bfd enable command, the BFD session is established with the specified

discriminator values. Such a BFD session is used to detect the connectivity of a pair of LSPs in

opposite directions (one from local to remote, and the other from remote to local) between two

devices.

• Dynamic—If you do not specify the local and remote discriminator values when configuring the bfd

enable command, the MPLS LSP ping is run automatically to negotiate the discriminator values and

then the BFD session is established based on the negotiated discriminator values. Such a BFD

session is used for connectivity detection of an LSP from the local device to the remote device.

Configuration prerequisites

Before enabling BFD for an LSP, complete the following tasks:

• Configure an IP address for the loopback interface, and configure the IP address as the MPLS LSR

ID of the device.

• Configure BFD session parameters on the loopback interface.

The device uses the BFD session parameters configured on the loopback interface to establish a BFD

session, and it uses the MPLS LSR ID as the source address of the BFD packets. For more information

about BFD, see High Availability Configuration Guide.

To establish a static BFD session, make sure there is already an LSP from the local device to the remote

device and an LSP from the remote device to the local device.

Configuration guidelines

• You cannot establish both a static BFD session and a dynamic BFD session for the same LSP.

• After a static BFD session is established, you cannot modify the discriminator values of the BFD

session.

• In a BFD session for detecting LSP connectivity, the ingress node always operates in active mode

and the egress node always operates in passive mode. The bfd session init-mode command does

not take effect on the ingress and egress nodes of such a BFD session. Even if you configure the two

nodes to both operate in passive mode, the BFD session can still be established successfully.

• BFD for MPLS LDP is for detecting the IP connectivity between two remote LDP peers. BFD for LSP is

for detecting the connectivity of LSPs.

Configuration procedure

To configure BFD for LSPs:

Ste

Command

Remarks

1. Enter system view.

system-view N/A

2. Enable LSP verification and

enter the MPLS LSPV view.

mpls lspv Not enabled by default.