to figure this out you need to go by route path selection rules that go in the process below and also how ospf choses best path selection
standard rules
- Prefix Length - The longest-matching route is preferred first. Prefix length trumps all other route attributes.
- Administrative Distance - In the event there are multiple routes to a destination with the same prefix length, the route learned by the protocol with the lowest administrative distance is preferred.
- Metric - In the event there are multiple routes learned by the same protocol with same prefix length, the route with the lowest metric is preferred. (If two or more of these routes have equal metrics, load balancing across them may occur.)
ospf path selection rules
Intra-Area (O)
Inter-Area (O IA)
External Type 1 (E1)
External Type 2 (E2)
NSSA Type 1 (N1)
NSSA Type 2 (N2)
One of the sides Is NSSA which will make it least preferred after the path selection rules , AD is the same , prefix length should be the same , metric cost looks to be the same , so it comes down to ospf path selection , NSSA is least preferred so I would think R1 would take r3 to r4 as its E2
