300-420 Question 218
Single answerAn enterprise network is connected to two different Internet Service Providers (ISPs) for redundancy and improved performance. The network administrator wants to ensure that outbound traffic uses the most optimal ISP path based on real-time link performance while maintaining failover capabilities. Which design approach should be implemented to achieve this in a multihomed environment?
- A
Use BGP with local preference to control outbound traffic and configure failover.
- B
Implement static routing with equal-cost multipath (ECMP) to both ISPs.
- C
Configure HSRP between the two ISP links to manage traffic redundancy.
- D
Use BGP with path prepending to prioritize one ISP for traffic and the other as a backup.
Show answer and explanation
Correct answer: A
Explanation
In a multihomed environment, BGP with local preference is the preferred method for optimizing outbound traffic based on real-time path performance while maintaining redundancy. Local preference allows administrators to define policies that prioritize one ISP over another for specific traffic flows, and BGP failover mechanisms ensure continuity if one ISP becomes unavailable. Other options, such as static routing, HSRP, or path prepending, do not offer the same level of control or adaptability in this scenario.
- A. Correct.
BGP with local preference is the correct approach for controlling outbound traffic in a multihomed environment. Local preference can be used to prefer one ISP over another for specific prefixes while also allowing failover if the preferred ISP becomes unavailable.
- B. Incorrect.
Static routing with ECMP does not provide the flexibility to dynamically manage traffic based on real-time link performance or prioritize specific ISPs for traffic. It also lacks robust failover capabilities in case one ISP experiences an issue.
- C. Incorrect.
HSRP is designed for high availability within a local network and is not suitable for managing traffic redundancy or path optimization across multiple ISPs.
- D. Incorrect.
BGP path prepending is primarily used to influence inbound traffic from external networks. While it can prioritize one ISP as a backup, it does not dynamically optimize outbound traffic based on performance.