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. All the BFD sessions use UDP port 6784 and destination MAC address 01-00-5E-90-00-01. 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 the 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 the 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 the 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.

To enable BFD for an aggregation group: