Link-down notifications enable the IP multipathing daemon to detect physical link failures faster. When a network interface is started, the IP multipathing daemon attempts to enable link-up and link-down notifications from the network interface driver. A link-down notification is generated when the interface detects the loss of the physical link to the network. A link-up notification is generated when the physical link is restored. The driver must support this feature in order for the notification procedure to work. The RUNNING flag is unset when a link-down notification is received, and set when a link-up notification is received. The IP multipathing daemon uses the RUNNING flag to monitor the physical link state.
For more information, see the IP network multipathing chapters in the System Administration Guide: IP Services.