DNS Failover Testing with Amazon Route 53

Correct Answer: A.

DNS Failover can be configured for Amazon ELB.

For this, an Alias record needs to be pointed at ELB, and “Evaluate Target Health” parameters need to be set as true.

Based upon these settings, Route 53 creates and manages health checks for ELB automatically.

Options B and D are incorrect as for DNS failover ELB endpoint, alias record needs to be created, not the CNAME record.

Option C is incorrect as there is no need to associate resource record sets with the health check.

This association is done automatically by Route 53.

For more information on DNS failover with ELB, refer to the following URL,

https://aws.amazon.com/route53/faqs/

Sure, I can help you understand the options and their implications.

To begin with, DNS failover testing refers to the ability to automatically redirect traffic from one endpoint to another in case of a failure. This can be useful to improve availability and reduce downtime for applications.

In the scenario described in the question, the web application is deployed on an EC2 instance that is front-ended by an ELB. This means that traffic from clients is routed to the ELB, which then forwards it to the EC2 instance(s) running the application. To perform DNS failover testing, we need to ensure that traffic can be redirected to a backup endpoint if the primary one is unavailable.

Amazon Route 53 is a DNS service that can be used to manage domain names and route traffic to various endpoints, including ELBs, EC2 instances, and other resources. It provides several options for configuring DNS failover, including the use of health checks and resource record sets.

Let's look at the four options provided in the question:

A. Create an Alias record pointing to ELB & set the “Evaluate Target Health” parameter to true.

An Alias record is a type of DNS record that can be used to map a domain name to an AWS resource, such as an ELB. When "Evaluate Target Health" is set to true, Route 53 performs health checks on the ELB to determine its availability. If the ELB is unavailable, Route 53 can automatically redirect traffic to a backup endpoint, such as another ELB or an EC2 instance.

B. Create a CNAME record pointing to ELB & set the “Evaluate Target Health” parameter to true.

A CNAME record is another type of DNS record that can be used to map a domain name to a hostname. In this case, the hostname would be the DNS name of the ELB. Again, setting "Evaluate Target Health" to true enables Route 53 to perform health checks and redirect traffic if the ELB is unavailable.

C. Create an Alias record pointing to ELB & associate resource record set for ELB with the health checks.

This option involves creating an Alias record for the ELB, as in option A, but also associating a resource record set (RRS) with the health checks. An RRS is a group of DNS records that share the same settings, such as TTL and routing policies. By associating the RRS with the health checks, we can specify additional routing rules that take effect when the ELB is unavailable.

D. Create a CNAME record pointing to ELB & associate resource record set for ELB with the health checks.

This option is similar to option C, but uses a CNAME record instead of an Alias record. As with option C, we can associate an RRS with the health checks to specify backup routing rules.

So which option is the best for DNS failover testing? It depends on the specific requirements of the application and the desired level of control over the routing policies.

Option A and B are simple and straightforward, and can be sufficient for many applications. They provide basic failover functionality based on the health of the ELB.

Option C and D are more flexible and allow for more advanced routing rules, such as routing traffic to different endpoints based on geographic location or other factors. They also require more setup and configuration, but can be useful for more complex applications.

In summary, the recommended option for DNS failover testing depends on the specific needs of the application. For basic failover functionality, options A or B may be sufficient. For more advanced routing rules, options C or D may be more appropriate.