Domain Name System (DNS)

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DNS is a networking protocol that translates human-readable domain names into IP addresses. It acts like a phone book, enabling users to access websites and resources using easily memorable domain names instead of IP addresses. Amazon Route 53 is a highly available and scalable managed DNS service …

Guide to Understanding Amazon Route 53 and DNS for AWS Solution Architect Examination

Amazon Route 53 is a scalable cloud Domain Name System (DNS) web service. It is designed to provide reliable and cost-effective routing to your applications, websites, and other resources.

Why it is Important?
Route 53 provides the ability to connect user requests to infrastructure running in AWS, which includes EC2 instances, Elastic Load Balancers, and S3 buckets. Not only that, but it also works well with non-AWS infrastructure.

What it is?
Simply put, think of Route 53 as the phone book of the internet. Humans access websites using domain names, while web browsers interact using IP addresses. Route 53 bridges this gap by translating domain names to IP addresses – this process is known as DNS lookup.

How it works?
When a user enters your website name, it's sent to the DNS service (in this case, Route 53). This service then translates the website name into an IP address. Then, it replies back to the user's browser with the IP. Assuming it's valid, the user's browser then serves the website.

Exam Tips: Answering Questions on Domain Name System (DNS)
1. Learn about Route 53's routing policies: It's important to comprehend the difference between Simple, Weighted, Latency, Failover, and Geolocation Routing Policies and to understand how to implement them.
2. DNS record types: Understanding what A, AAAA, CNAME, and MX records are and when to use them will be beneficial while answering DNS-related questions.
3. Understand DNS hierarchy: Knowledge about how DNS hierarchy works, along with an understanding of root and TLD servers, SOA, and NS records, can help answer related questions.
4. Concept of DNS hostnames and domains: Understanding the difference between fully qualified domain names (FQDN), sub-domains and apex or root domains can help answer questions.

To summarize, a solid understanding of Route 53 and the DNS service will help you to decode DNS capabilities, answer DNS-related questions, and suggest architectures based on the requirement in the AWS Solution Architect Exam.

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Question 1

An organization using Amazon Route 53 needs to route end-user traffic to application instances closest to the user by geolocation. Which Route 53 routing policy should be used?

Geolocation routing Weighted routing Simple routing Latency-based routing

Correct Answer: Geolocation routing

Geolocation routing in Amazon Route 53 routes traffic based on the geographic location of end-users. This policy is the best choice for directing users to the application instances closest to their location.

Question 2

An Amazon S3 bucket is configured for static website hosting using the S3 website endpoint. The main HTML page loads, but several image URLs consistently return HTTP 403 AccessDenied. S3 Block Public Access is disabled, and there is no CloudFront or WAF in front of the bucket. What is the most likely cause?

Disabled AWS WAF Incorrect bucket policy Incompatible instance type Route 53 is not configured

Correct Answer: Incorrect bucket policy

For an S3 static website to serve images publicly, the bucket must allow anonymous s3:GetObject access to the object keys. If HTML loads but image requests return 403 AccessDenied, and S3 Block Public Access is disabled, the most likely cause is a missing or misconfigured bucket policy that does not grant public read (or includes an explicit Deny) for those objects. Route 53 misconfiguration would cause DNS resolution issues rather than an S3 403, EC2 instance types are irrelevant to S3 static hosting, and a disabled WAF would not block content.

Question 3

A network administrator is troubleshooting a slow internal website hosted on the company's on-premise data center. They suspect that the internal DNS server is causing the issue. What should the network administrator focus on?

Disable DNS server caching. Change the website's domain name. Switch to a public DNS server. Check DNS server caching and configuration.

Correct Answer: Check DNS server caching and configuration.

The best answer is to check the DNS server caching and configuration. If the internal DNS server is causing the website to be slow, it's likely due to issues with caching or misconfiguration. The administrator should review the DNS server settings, ensure the records are correct, and verify that caching is working properly. Changing the website's domain name would not address the underlying DNS issue. Disabling DNS caching altogether could actually worsen performance by requiring every request to be resolved by the DNS server. Switching to a public DNS server is unnecessary for an internal website and would not solve problems with the internal DNS server.

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