In the exhibit, R1 and R2 have a static default route configured that points toward the provider. Both routers redistribute the default route into OSPF. R2 is the preferred gateway to reach the provider. R1 is the backup gateway. All link metrics are equal.Which two steps ensure that traffic to the provider flows through R2 while the network is working properly? (Choose two.)
A.
Redistribute the default route as a Type 1 external route on router R1 and a Type 2 external route on router R2.
B.
Redistribute the default route as a Type 2 external route on router R1 and a Type 1 external route on router R2.
C.
Modify the preference value of the default route on router R1 so that it is less preferred than OSPF external routes.
D.
Modify the preference value of the default route on router R2 so that it is more preferred than OSPF external routes.
answer should be a&c because when R1 advertises external type 1 routes and R2 adverised external Type 2 route, prefered path is R2 because Type 1 external routes refect the total cost in the path, whereas Type 2 routes reflect the cost from ASBR to the destination.
In between Typ1 and Type 2 always type is preferred because it has internal+external cost knowledge. R2 is default gateway so it should have type 1 route.
Typo in above comment pls check this one.
In between Typ1 and Type 2 always type1 is preferred because it has internal + external cost knowledge. R2 is default gateway so it should have type 1 route.
I think B and C.
Ext1 is preferred over Ext2
See this webside:
http://packetcorner.wordpress.com/2012/08/20/ospf-route-selection-process/
This should be B and C.
Why?
By default, the static routes will be redistributed as both Type 2 external routes, And at that point will prefer the shortest path possible to the provider network for them.
Type 1 external routes are prefered over Type 2 so
we want to convert the route being sent out from R2 to a Type 1 external route.
(This will influence traffic from R3 and R4 to go out via R2)
(This will NOT influence LOCAL traffic from R1 to the provider)
So because R1 is configured with it’s own static route, the default preference will be 5 whereas the advertised preference from R2 will be 150.
To correct this, we will need to change the preference on the static route on R1 to be higher than 150 so it sees the default route being
advertised from R2 as a better route and keep it’s original route as a secondary route in the routing table.