Initial Configurations for OSPF over Non-Broadcast Links
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a008009470d.shtml#config2
http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a0080094054.shtml
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a008009470d.shtml#config2
Administrative distance is the first criterion that a router uses to determine which routing protocol to use if two protocols provide route information for the same destination. Administrative distance is a measure of the trustworthiness of the source of the routing information. Administrative distance has only local significance, and is not advertised in routing updates.