29.6.1 Overview

The multiple failure monitoring function monitors multiple failures of the shared link monitoring ring in a multi-ring configuration with a shared link, and switches the route to the shared link non-monitoring ring when multiple failures are detected. In this case, the shared link non-monitoring ring used to switch routes is called a backup ring.

The targets of detection by the multi-fault monitoring functionality are shared link faults, other link faults within shared link monitoring rings, and device faults accompanying link faults.

The following shows an example of a fault on a shared link monitoring ring, as well as the combination of faults that can be detected by the multi-fault monitoring functionality.

Figure 29-30: Example of a failure occurring in a shared link monitoring ring

Table 29-4: Combinations of failures that can be detected by the multiple failure monitoring facility

Failure type	Detectable combinations
Link fault	Link fault 1 (shared link fault)	Link fault 2 (other link fault)
	Link fault 1 (shared link fault)	Link failure 3 (other link failure)
	Link fault 1 (shared link fault)	Link failure 4 (other link failure)
Device fault	Device fault 1 (shared node fault) only
	Device failure 4 (shared node failure) only
	Device fault 2 (transit node fault)	Link fault 1 (shared link fault)
	Switch failure 3 (transit node failure)	Link fault 1 (shared link fault)