This read-write Unsigned32 identifies the specific ifIndex a line-password login history entry applies to, where 0 means the entry applies to all interfaces, and for the console port type the value can only be 0. An admin cares because it lets line-password login tracking be scoped either device-wide or to one particular physical interface, such as one Telnet-capable line versus another. For example, an admin wanting to track line-password logins only on a specific auxiliary port would set this to that port's ifIndex rather than 0.