300-410 Question 74
Single answerA network engineer is configuring a branch router with two WAN links to the headquarters. Link1 has a bandwidth of 100 Mbps, and Link2 has a bandwidth of 50 Mbps. The engineer wants to configure load balancing so that traffic is distributed across the two links in proportion to their bandwidth. Which configuration approach should be used?
- A
Configure EIGRP with variance to allow unequal-cost load balancing.
- B
Enable OSPF and configure ECMP (Equal-Cost Multi-Path) for equal-cost load balancing.
- C
Implement BGP with weight attributes to prefer one link over the other.
- D
Configure static routes with equal administrative distances for both links.
Show answer and explanation
Correct answer: A
Explanation
To achieve load balancing that distributes traffic proportionally to the bandwidth of the links (unequal-cost load balancing), EIGRP's variance feature is the best choice. OSPF and static routes are limited to equal-cost load balancing, while BGP weight attributes are not used for load balancing at all.
- A. Correct.
This is the correct answer. EIGRP's variance feature allows unequal-cost load balancing by permitting traffic to be sent over multiple paths proportional to their metrics (e.g., bandwidth).
- B. Incorrect.
This is incorrect because OSPF performs only equal-cost load balancing. Since the two links have different bandwidths, OSPF ECMP is not suitable for this scenario.
- C. Incorrect.
This is incorrect because BGP weight attributes are used for path preference, not load balancing. It will not distribute traffic proportionally across multiple links.
- D. Incorrect.
This is incorrect because static routes with equal administrative distances would only allow equal-cost load balancing, not bandwidth-proportional load balancing.