Enabling BFD for an aggregation group

BFD for Ethernet link aggregation can monitor member link status in an aggregation group. After you enable BFD on an aggregate interface, each Selected port in the aggregation group establishes a BFD session with its peer port. BFD operates differently depending on the aggregation mode.

• BFD for static aggregation—When BFD detects a link failure, BFD notifies the Ethernet link aggregation module that the peer port is unreachable. The local port is placed in Unselected state. The BFD session between the local and peer ports remains, and the local port keeps sending BFD packets. When the link is recovered, the local port receives BFD packets from the peer port, and BFD notifies the Ethernet link aggregation module that the peer port is reachable. The local port is placed in Selected state again. This mechanism ensures that the local and peer ports of a static aggregate link have the same aggregation state.

• BFD for dynamic aggregation—When BFD detects a link failure, BFD notifies the Ethernet link aggregation module that the peer port is unreachable. BFD clears the session and stops sending BFD packets. When the link is recovered and the local port is placed in Selected state again, the local port establishes a new session with the peer port. BFD notifies the Ethernet link aggregation module that the peer port is reachable. Because BFD provides fast failure detection, the local and peer systems of a dynamic aggregate link can negotiate the aggregation state of their member ports faster.

For more information about BFD, see High Availability Configuration Guide.

When you enable BFD for an aggregation group, follow these restrictions and guidelines:

• Make sure the source and destination IP addresses are consistent between the two ends of an aggregate link. For example, if you execute link-aggregation bfd ipv4 source 1.1.1.1 destination 2.2.2.2 at the local end, execute link-aggregation bfd ipv4 source 2.2.2.2 destination 1.1.1.1 at the peer end. The source and destination IP addresses cannot be the same.

• The BFD parameters configured on an aggregate interface take effect on all BFD sessions in the aggregation group. BFD sessions for link aggregation do not support the echo packet mode or the Demand mode.

• As a best practice, do not configure other protocols to collaborate with BFD on a BFD-enabled aggregate interface.

• Make sure the number of member ports in a BFD-enabled aggregation group is less than or identical to the number of BFD sessions supported by the device. If the aggregation group contains more member ports than the supported sessions, some Selected ports might change to the Unselected state.

• If the number of BFD sessions differs between the two ends of an aggregate link, check their settings for inconsistency in the maximum number of Selected ports. You must make sure the two ends have the same setting for the maximum number of Selected ports.

1. Enter system view.

   system-view

2. Enter Layer 2 aggregate interface view.

   interface bridge-aggregation interface-number

3. Enable BFD for the aggregation group.

   link-aggregation bfd ipv4 source ip-address destination ip-address

   By default, BFD is disabled for an aggregation group.