300-420 Question 222
Single answerAn enterprise has deployed a primary MPLS circuit for its WAN connectivity between branch offices and the data center. To ensure business continuity, they want to implement a backup connectivity solution. The backup link must automatically take over in case of a primary link failure, and the solution should prioritize cost efficiency while maintaining connectivity. Which solution would best meet these requirements?
- A
Implement a secondary MPLS circuit with equal cost multipath (ECMP) routing enabled.
- B
Deploy an internet-based VPN as the backup link and configure IP SLA with tracking to fail over automatically.
- C
Use a dedicated leased line for backup connectivity and configure BGP with a higher local preference for the primary link.
- D
Configure a 4G/LTE cellular link as the backup and use static routing with administrative distance to control failover.
Show answer and explanation
Correct answer: B
Explanation
The best solution is to deploy an internet-based VPN as the backup link and configure IP SLA with tracking. This approach is cost-effective since internet connections are generally cheaper than MPLS or leased lines. IP SLA with tracking ensures automatic failover, maintaining connectivity in case of a primary link failure. The other options either fail to meet the cost efficiency or failover automation requirements.
- A. Incorrect.
Implementing a secondary MPLS circuit with ECMP would provide redundancy, but it is not cost-efficient as the backup circuit would be underutilized and ECMP does not differentiate between primary and backup circuits. This does not meet the cost prioritization requirement.
- B. Correct.
Deploying an internet-based VPN as the backup link is a cost-effective solution. Using IP SLA with tracking ensures automatic failover when the primary MPLS link fails, meeting both the cost and failover requirements.
- C. Incorrect.
A dedicated leased line would provide reliable backup connectivity, but it is expensive and not aligned with the cost prioritization requirement. Configuring BGP with local preference can ensure primary usage, but it does not address the need for cost efficiency.
- D. Incorrect.
A 4G/LTE cellular link can serve as a backup option, but static routing with administrative distance does not provide the same level of responsiveness as IP SLA with tracking. Additionally, cellular links might have higher latency and data costs, making it less ideal in this scenario.