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If any router recived tow routing updates,one from RIP and other from OSPF ,the router would need a way to choose one update over the other
If the router has more than one route for same destination , It will check longest prefix match and thereafter smaller AD value for the given two routing protocol.
Best Route is placed in Routing table of router.More Specific routes are first placed and then comes Administrative distance in below sequence:
Connected interface 0 Static route 1 Enhanced Interior Gateway Routing Protocol (EIGRP) summary route 5 External Border Gateway Protocol (BGP) 20 Internal EIGRP 90 IGRP 100 OSPF 110 Intermediate System-to-Intermediate System (IS-IS) 115 Routing Information Protocol (RIP) 120 Exterior Gateway Protocol (EGP) 140 On Demand Routing (ODR) 160 External EIGRP 170 Internal BGP 200 Unknown* 255
for multi Routing Protoclo enviroment Administrative Distance(AD) is used as a tie Breaker if a route recive two route with different metrics
1) RIP with hop count3( metric3)
2) EIGRP with metric1213555
the route do not compare the two metrics since this metric are calculated with different algorism so the router choose the route with low Administartive distance which is EIGRP Route
look below AD of some Routing Protocol
Protocol Administrative Distance
RIP 120
OSPF 100
EIGRP 90
IS-IS 115
by adminstrative distance and using routing table its update
OSPF because it is cost effective approach
If a router has two or more than two routes for same destination in routing table :
the first thing that will mater is : which one of them is the longest match,
2nd will be the lower adminitrative distance value assigned to routing protocol.
for your reference
Connected routes :0
static Routes :1
RIP :120
EIGRP :90
OSPF :110
IBGP:200
EBGP :20