Explanation/Reference:
Explanation:
What Is Administrative Distance?
Select the Best Path
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.
Note: The smaller the administrative distance value, the more reliable the protocol. For example, if a router
receives a route to a certain network from both Open Shortest Path First (OSPF) (default administrative
distance -110) and Interior Gateway Routing Protocol (IGRP) (default administrative distance -100), the
router chooses IGRP because IGRP is more reliable.
This means the router adds the IGRP version of the route to the routing table.

Reference: http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094195.shtml