This INTEGER object controls the optional Key field in outgoing GRE packet headers, choosing disabled(1) to omit it, provisioned(2) to use a manually configured value, or generated(3) to let the CPE generate its own key. An engineer sets it depending on whether the remote concentrator requires a specific, coordinated key value or can accept a device-generated one. For example, a concentrator that demands a specific pre-shared key value for this tunnel would require setting this to provisioned(2) and supplying that exact value in clabGRETunnelInterfaceKeyIdentifier.