The 7705 SAR supports the application of BFD to monitor individual LAG link members in order to speed up the detection of link failures. When BFD is associated with an Ethernet LAG, BFD sessions are set up over each link member. These asynchronous independent sessions are referred to as micro-BFD sessions. When micro-BFD is configured, a link is not operational in the associated LAG until the associated micro-BFD session is fully established. The link member is taken out of the operational state in the LAG if the micro-BFD session fails.
Although ETH-EFM can be used on individual LAG links, EFM timers are limited to 100 ms. With micro-BFD, 10-ms timers are supported, which allows for much faster detection times. The micro-BFD sessions use the well-known destination UDP port 6784 over LAG links. The source MAC address is the local system MAC address for the LAG interface. The micro-BFD packets use the well-known destination MAC address 01:00:5e:90:00:01.