If you’re studying for an AWS certification exam, Route 53 is likely to be one of the topics you’ll encounter. This service plays a crucial role in connecting your web applications and services to the internet, and it provides various features for routing traffic, managing domain names, and monitoring health checks. In this post, I’ll share some exam notes on Route 53 that will help you prepare for the exam and understand the key concepts and terminology associated with this service. Let’s dive in!

Route 53

Route 53 Policies

Simple Routing Policy

• When using the simple routing policy, you’re limited to having one record with multiple IP addresses. If you include multiple values in a record, Route 53 will randomly return one of the IP addresses to the user each time they request the record.
• The simple routing policy is useful when you have a single resource that can handle all the traffic, or multiple resources that have equivalent capabilities and are interchangeable. It is also easy to configure and requires minimal setup.
• The simple routing policy does not perform any health checks on the resources associated with the record set. As a result, if a resource becomes unhealthy, Route 53 will continue to return its IP address in the DNS response, potentially leading to degraded performance or downtime for the end users.

Weighted Routing Policy

• This policy allows you to route traffic to multiple AWS resources based on a specified weighting.
• The Weighted Routing Policy also allows you to perform health checks on the resources, so that you can automatically route traffic to the healthy resources. If a resource fails its health check, Route 53 will stop routing traffic to it until it becomes healthy again. When you create a health check, you can configure Amazon CloudWatch Alarms to monitor the health check and send alerts when the health check fails.

Failover Routing Policy

• The failover routing policy is a type of DNS routing policy in Route 53 that allows you to configure a primary resource and a secondary resource for a particular record. When the primary resource is healthy, Route 53 will route traffic to the primary resource. However, if the primary resource becomes unavailable or unhealthy, Route 53 will automatically failover to the secondary resource.
• Allows you to perform health checks.

Geolocation Routing Policy

• The geolocation routing policy is a type of DNS routing policy in Route 53 that allows you to route traffic to specific resources based on the geographic location of the user making the DNS query. This policy can be useful for scenarios where you want to serve content or applications that are optimized for users in specific regions.
• Doesn’t allow you to perform health checks.

Geoproximity Routing Policy

• The geoproximity routing policy is similar to the geolocation routing policy in that it allows you to route traffic to specific resources based on the geographic location of the user making the DNS query. However, the geoproximity routing policy also takes into account the health of the resources, whereas the geolocation routing policy does not.
• In the geoproximity routing policy, you can also specify a routing bias, which is the percentage of traffic that should be sent to each resource. This can be useful for scenarios where you want to ensure that a certain resource receives a larger share of the traffic.
• To use geoproximity routing, you must use Route53 traffic flow.

Latency Routing Policy

• The latency routing policy is a type of DNS routing policy in Route 53 that allows you to route traffic to resources based on the lowest network latency to the user. This policy can be useful for scenarios where you want to serve content or applications from the resource that is closest to the user to minimize network latency and improve performance.
• Allows you to perform health checks.

Multivalue Answer Routing Policy

• This policy allows you to specify multiple values for a record, and Route 53 will respond to DNS queries with those values in a random order (Similar to Simple Routing Policy).
• You can also configure health checks for each record to ensure that only healthy resources are included in the DNS response.

Reference Topics

Domain Name System (DNS)

• DNS stands for Domain Name System. It is a system that is used to translate human-friendly domain names, such as www.example.com, into IP addresses that computers can understand, such as 192.0.2.1.
• When a user types a domain name into their web browser, the browser sends a request to a DNS resolver (usually operated by the user’s ISP or another third-party DNS service). The resolver then queries a series of DNS servers to find the IP address associated with the domain name, and returns it to the user’s browser, which then connects to the website or resource using the IP address.
• DNS is a distributed system, with millions of DNS servers all over the world, working together to provide efficient and accurate translation of domain names into IP addresses.

Top-Level Domain (TLD)

• A top-level domain (TLD) is the last part of a domain name in a web address, which follows the final dot. For example, in the domain name “example.com”, the TLD is “.com”.
• TLDs are divided into two categories: generic TLDs (gTLDs) and country code TLDs (ccTLDs). Some examples of gTLDs include .com, .org, and .net, while some examples of ccTLDs include .ca for Canada, .uk for United Kingdom, and .jp for Japan.
• In addition to these standard TLDs, there are also newer TLDs, called new generic TLDs (ngTLDs) that have been introduced in recent years. These include extensions like .app, .blog, .club, and .guru, among others.
• TLDs are managed by the Internet Assigned Numbers Authority (IANA), which is responsible for the global coordination of the DNS root, IP addressing, and other internet protocol resources. The IANA delegates the management of TLDs to various organizations, including country code managers and private companies.
• View TLDs – http://www.iana.org/domains/root/db

Domain Registrars

• A domain registrar is a company or organization that manages the reservation of domain names for websites. They are responsible for registering domain names, maintaining the domain name system (DNS) and providing domain name services such as domain name registration, domain name transfer, and DNS hosting.
• Domain registrars are accredited by the Internet Corporation for Assigned Names and Numbers (ICANN) and are required to follow specific guidelines and policies to ensure the stability and security of the internet’s domain name system.
• Some popular domain registrars include GoDaddy, Namecheap, Google Domains, AWS Route 53, and Bluehost, among others.

DNS Record Types

• A (Address) Record
  • Maps a domain name to an IP address.
  • For example, if you enter the domain name “example.com” in a web browser, the browser sends a request to a DNS server to translate the domain name to an IP address. The DNS server looks up the A record for “example.com” and returns the corresponding IP address, such as “192.0.2.1”.
• AAAA Record
  • Maps a domain name to an IPv6 address.
• CNAME (Canonical Name) Record
  • Maps an alias or subdomain to the canonical domain name.
  • For example, if you have a website hosted on a server with the domain name “example.com”, you can create a CNAME record that maps a subdomain like “www” to the canonical domain name. This means that when a user types in “www.example.com” into their web browser, the DNS system will look up the CNAME record and redirect the user to the canonical domain name of “example.com”.
• SOA (Start of Authority) Record
  • Specifies administrative information about a DNS zone, including the primary name server and contact information.
  • The SOA record contains several pieces of information, including the primary name server for the zone, the email address of the administrator responsible for the zone, and a serial number that is used to track changes to the zone file. The SOA record also includes other optional parameters, such as the time-to-live (TTL) for the zone and the refresh, retry, and expire intervals. These intervals determine how often other name servers should check for updates to the zone and how long they should cache information about the domain name and its associated DNS records.
• NS (Name Server) Record
  •  Specifies the name servers for a domain name.
  • When a client sends a DNS query for a domain name, the resolver looks up the NS records for that domain name to find out which name servers are authoritative for the domain. Once it has this information, the resolver can query one of the authoritative name servers to obtain the DNS records for the domain.
• MX (Mail Exchange) Record
  • Specifies the mail server responsible for accepting email messages for a domain name.

Alias Record vs CNAME

• Alias records can be used to map a domain name to a specific AWS resource, such as an Amazon S3 bucket or CloudFront distribution, whereas CNAME records are typically used to map one domain name to another, such as mapping “www.example.com” to “example.com”.
• Alias can be used for a naked domain name (zone apex record), whereas CNAME cannot be used for naked domain names. You can’t have a CNAME for http://example.com.

TTL (Time to Live)

• TTL stands for “Time to Live” and refers to the amount of time that a DNS record is cached on a DNS resolver or a client’s local system before it is refreshed from the authoritative DNS server. In other words, it is the period of time that a DNS record is valid and can be cached by a resolver.
• When a DNS resolver receives a request for a DNS record, it first checks if it has a cached copy of the record. If it does, and the TTL has not expired, it returns the cached record to the client. If the TTL has expired, the resolver queries the authoritative DNS server for the updated record and caches it for the new TTL.
• The TTL value is set by the owner of the DNS record and can be adjusted based on their needs. A shorter TTL means that changes to a DNS record will propagate faster, but it also means that the DNS resolver will have to query the authoritative DNS server more frequently, which can increase network traffic. Conversely, a longer TTL means that changes will take longer to propagate, but reduces the number of queries made to the authoritative DNS server.

I hope you found these exam notes on Route 53 useful for your AWS certification exam preparation. If you want to learn more about other AWS services and topics related to the SAA-C03 exam, be sure to check out some of our other posts on this blog. I cover various aspects of AWS architecture, security, storage, networking, and more, with a focus on helping you ace the exam and become a certified AWS Solutions Architect Associate. Thank you for reading, and stay tuned for more content!