Administrative distance (AD) measures the trustworthiness of a routing information source. Lower values are more trusted.
When the same destination is learned from multiple sources (e.g., static route and OSPF), the router installs only the route with the lowest AD.
Default AD values:
- Connected:
- Static:
- EIGRP summary:
- External BGP:
- EIGRP:
- OSPF:
- IS-IS:
- RIP:
- External EIGRP:
- Internal BGP:
AD is a local configuration. It doesn't travel with routing updates. You can modify AD to influence route selection on individual routers.