This field, also known as administrative distance, specifies the preference value used to select among multiple routes to the same destination prefix, with a smaller value being more preferred. An admin tunes this to control which of several available paths, say a static route versus an OSPF-learned route to the same prefix, the device actually installs as active. Configuring a static backup route with a higher preference value than the OSPF-learned primary route ensures OSPF is used whenever it's available.