Reports the live tunnel-testing or link-probe result, alive, dead, or unknown, for this Permanent Tunnel, separate from its IKE-negotiation state. Because permanent tunnels are relied upon to always be passing traffic, this is the field that catches the specific failure mode where the tunnel is negotiated, state active, but the data path itself has silently died, arguably more important to watch here than on ordinary tunnels precisely because nothing else is supposed to fail over to cover for it. Example: permanentTunnelProbState reporting dead(2) while permanentTunnelState still shows active(3) for a disaster-recovery link means traffic depending on that always-up tunnel is actually failing silently, a scenario worth its own dedicated alert.