This is the count of tunnel instances currently switched over onto their detour LSP (under oneToOneBackup) or of tunnels actively being switched over (under facilityBackup). Because it reflects live failover state rather than configured capability, a nonzero and climbing value directly indicates that the link or node this router was protecting against has actually failed and traffic is now flowing over backup paths instead of the primary. For example, if a fiber cut on this router's primary uplink triggers all 8 protected tunnels to reroute, this value jumps to 8 until the primary path is restored and traffic switches back.