This object is a read-write boolean controlling Loop Guard, which prevents alternate and root ports from erroneously transitioning into designated ports: in SSTP/PVST a Loop Guard-enabled designated port is always blocked, and in RSTP/MSTP a Loop Guard-enabled port that becomes designated because it stopped receiving BPDUs is blocked. Administrators enable it to guard against Layer 2 loops caused by a unidirectional link failure that stops BPDUs from arriving. For example, enabling stpOptfLoopGuard on redundant fiber uplinks prevents a bridging loop if one strand of a fiber pair fails silently.