Which routing protocol has the smallest default administrative distance?

Default Distance Value TableThis table lists the administrative distance default values of the protocols that Cisco supports:

Route Source –

Default Distance Values –

Connected interface –

Static route –
Enhanced Interior Gateway Routing Protocol (EIGRP) summary route External Border Gateway Protocol (BGP)

Internal EIGRP –

IGRP –

OSPF –
Intermediate System-to-Intermediate System (IS-IS) Routing Information Protocol (RIP) Exterior Gateway Protocol (EGP)
On Demand Routing (ODR)

External EIGRP –

Internal BGP –
Unknown*
Reference:
http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/15986-admin-distance.html