This read-write value sets the administrative distance used for OSPF Autonomous System external routes, meaning routes imported into OSPF from another routing source. An admin often sets this higher than the OSPF internal distance so genuinely internal OSPF routes are preferred over redistributed external ones covering the same destination. For example, giving OSPF external routes a higher distance than OSPF internal routes prevents a redistributed static route from displacing a native OSPF route to the same network.