300-420 Question 219
Single answerAn enterprise has deployed a multihomed network with connections to two different ISPs. The network administrator wants to ensure high availability and load sharing between the ISPs for outbound traffic, while also ensuring a failover mechanism in case one ISP link fails. Which approach should the administrator take to achieve this?
- A
Configure BGP with AS path prepending to influence outbound traffic.
- B
Use static routing and distribute traffic equally across both ISP links.
- C
Implement BGP with dual-homed connections using different AS numbers for each ISP.
- D
Enable policy-based routing (PBR) to manually define traffic paths for both ISPs.
Show answer and explanation
Correct answer: C
Explanation
BGP is the most appropriate protocol for managing multihomed networks because it supports dynamic routing, load sharing, and automatic failover. By configuring BGP with dual-homed connections and leveraging its routing capabilities, the enterprise can achieve the desired goals of high availability and outbound traffic load sharing. Other options, such as static routing or policy-based routing, lack the dynamic adaptability and scalability required for multihomed environments.
- A. Incorrect.
Configuring BGP with AS path prepending is primarily used to influence inbound traffic rather than outbound traffic. While it can provide some control over routing, it does not inherently enable load sharing or dynamic failover for outbound traffic.
- B. Incorrect.
Static routing lacks the dynamic capabilities required for failover and load sharing. It cannot automatically adapt to link failures, making it unsuitable for multihomed setups requiring high availability.
- C. Correct.
Implementing BGP with dual-homed connections and using different AS numbers for each ISP allows the enterprise to dynamically exchange routing information, enabling load sharing and failover. BGP's capabilities make it the most suitable solution for multihomed environments.
- D. Incorrect.
Policy-based routing (PBR) can define specific traffic paths but requires extensive manual configuration and maintenance. It also does not inherently provide dynamic failover capabilities, making it less ideal for this scenario.