Administrative distance is then used as a tie breaker
to determine which way to go when multiple routing protocols
tell the router to go different ways.
as an analogy, administrative distance is used as a tie breaker
to determine which way to forward the traffic
if OSPF says go left and EIGRP says go right
the router uses administrative distance
to determine which routing protocol it believes most.
Technically, what happens is that the routing protocol
with the lowest administrative distance is more believable
and its routing information is inserted into the RIB
or Routing Information Based or routing table in preference
of other routing protocols that have a higher administrative distance
so EIGRP has a lower administrative distance than OSPF.
EIGRP has an administrative distance of 90
OSPF has an administrative distance of 110
so internal EIGRP would be preferred over OSPF.
So the lower the administrative distance
the more believable a routing protocol is
you cannot believe anyone more than yourself
so a router will believe routes that it originates
above routes received from neighboring devices.
A directly connected interface has a believability factor
or administrative distance of 0.
A static route configured to a next hop IP address
has an administrative distance of 1.
When a static route is configured to a directly connected interface
it is deemed to be directly connected
and therefore has a believability factor or administrative distance of 0.
The reason why static routes have such a low administrative distance
is that the router believes that you know more than other routers do.
You as the administrator are supposed to know what you're doing
and thus the router believes you more than it believes
routes received via routing protocols such as OSPF or EIGRP.
EIGRP has administrative distance of 90 for internal routes
those are routes that originated in EIGRP and will not be redistributed
or taken from a different routing protocol and then put into EIGRP.
OSPF has an administrative distance of 110
RIP has an administrative distance of 120
and unknown routes have an administrative distance of 255
as you can see EIGRP has a lower administrative distance than RIP does
and that’s because EIGRP is a better or more powerful routing protocol.
EIGRP will take bandwidth and delay into account when determining the best route.
RIP only uses hop count
so EIGRP seems to be better than OSPF which is better than RIP.