300-420 Question 220
Single answerAn enterprise network is designed with dual WAN connections to provide backup connectivity for critical business operations. The primary connection uses MPLS, while the backup connection uses a broadband internet link. The network engineer wants to ensure that the backup link is only used when the primary MPLS connection fails. What is the MOST effective configuration to achieve this?
- A
Configure static routes with a higher administrative distance for the backup broadband link.
- B
Use equal-cost multipath routing (ECMP) to load balance traffic across both links.
- C
Implement a routing protocol, such as OSPF, with manual route redistribution for failover.
- D
Configure IP SLA with tracking to dynamically route traffic to the backup link upon primary link failure.
Show answer and explanation
Correct answer: D
Explanation
IP SLA with tracking is the most effective solution for backup connectivity because it provides dynamic monitoring of the primary link and automates failover to the backup link when a failure is detected. This minimizes downtime and ensures the backup link is only used when necessary, aligning with the enterprise's requirements for redundancy and reliability.
- A. Incorrect.
Using static routes with a higher administrative distance for the backup link ensures it is used only when the primary route is unavailable. However, this approach does not dynamically detect link status or performance issues, making it less flexible and reliable.
- B. Incorrect.
Equal-cost multipath routing (ECMP) is used for load balancing across multiple paths of equal cost. This does not meet the requirement to use the backup link only when the primary connection fails.
- C. Incorrect.
Implementing a routing protocol with manual redistribution can provide failover options, but it is a complex approach that is not specifically designed for dynamic failover between primary and backup links.
- D. Correct.
Using IP SLA with tracking is the most effective solution because it allows the network to monitor the primary link's status and automatically reroute traffic to the backup link when the primary link fails, ensuring seamless failover.