jnxStaticMacIfIndex is a read-only InterfaceIndex that, together with jnxStaticMacAddress, indexes the table listing which interfaces a given statically-bypassed MAC address is permitted to appear on. Admins use this to restrict a MAC-authentication-bypass entry to specific physical ports, so the static bypass only applies where that device is expected to be connected rather than anywhere on the switch. For example, an admin might restrict a printer's bypass MAC address to only the ifIndex of the port it's physically wired into, so the bypass can't be exploited by plugging a spoofed-MAC device into a different port.