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Question 51

Refer to the exhibit. Routers R1, R2, R3, and R4 have been configured to run OSPF, and router R5 is running EIGRP. Traffic from R1 to R5 is expected to pass via R4, but OSPF routing has calculated the best path R3. Which action corrects the problem?

    Correct Answer: D

    When redistributing EIGRP into OSPF, the metric type plays a critical role in path selection. OSPF uses two types of external metrics: E1 and E2. E1 adds the internal OSPF cost to the redistributed route cost, while E2 uses only the redistributed route cost, regardless of the internal OSPF cost. Since R3 is configured to redistribute EIGRP as metric-type 1 (E1), it results in OSPF choosing the path via R3 over R4 because E1 is generally preferred over E2. Changing the metric-type on R3 to 2 (E2) makes it equal in preference to R4, which is already using metric-type 2. Thus, OSPF can then consider the actual path cost and select the desired path through R4.

Discussion
SeeleOption: B

EIGRP Metric Type 1 is preferred over Type 2 Traffic is expected to pass via R4, but because of the metric type configured, R3 is preferred. We can assume that traffic manipulation is already configured to prioritize R4.

thejag

If both R3 and R4 redistribute the EIGRP as E2 routes, how do we know that R4 will be a lower metric? It doesn't give us the details ospf costs on the R2 links.

NC9337

Yes, but the most used link today is over 100mbit, so we maybe can assume the total cost for R1 to R3 is 2 using type 1. And since E2 default redist eigrp as cost of 20. The only possible solution i see with this limited info is tho redis eigrp with type one metric of 20 (higher than R3) would gives path via R3 22 and via R4 20.

NC9337

Nvm, forgott E1 is prefered over E2. Static wont work either, not r1 in a0 either.