What is Administrative Distance or How Router 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.
Route Source and its AD
Connected 0
Static 1
External BGP (Border Gateway Protocol) 20
Internal EIGRP (Enhanced IGRP) 90
IGRP (Internet Gateway Routing Protocol) 100
OSPF (Open Shortest Path First) 110
IS-IS (Intermediate System to Intermediate System) 115
RIP (Routing Information Protocol) 120
ODR (On Demand Routing) 160
External EIGRP 170
Internal BGP 200
Unknown 255
Static 1
External BGP (Border Gateway Protocol) 20
Internal EIGRP (Enhanced IGRP) 90
IGRP (Internet Gateway Routing Protocol) 100
OSPF (Open Shortest Path First) 110
IS-IS (Intermediate System to Intermediate System) 115
RIP (Routing Information Protocol) 120
ODR (On Demand Routing) 160
External EIGRP 170
Internal BGP 200
Unknown 255
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