Amazon Web Services (AWS) Route 53 is a versatile and powerful DNS web service that allows users to manage and route their traffic effectively. When it comes to routing policies, there are two primary options: Simple Routing and Multivalue Answer Routing. Each policy has its own use cases and advantages, making it essential to understand when and why to use them.
Simple Routing Policy:
When to Use:
Simple Routing is ideal for straightforward DNS scenarios where you need to route traffic to a single resource, such as a website’s web server. It’s also suitable when dealing with a single record that contains multiple values, like an A record specifying multiple IP addresses.
How it Works:
With Simple Routing, AWS Route 53 returns the values in a random order to the client. You cannot influence the order, weight the records, or attach a health check to this policy.
Example:
Let’s say you have a domain, “www.example.com,” and you’ve created an A Record with multiple IP addresses:
- www.example.com A Record 192.0.2.1 60
- 198.51.100.1 60
- 203.0.113.1 60
When a client makes a DNS request, Route 53 will return all three IP addresses, but in a random order. It’s essential to note that, with Simple Routing, even if one of the IP addresses is unhealthy, Route 53 will still return it to the client, potentially causing downtime for the user.
Multivalue Answer Routing Policy:
When to Use:
Multivalue Answer Routing is designed for more complex DNS setups. It’s useful when you’re creating multiple records of the same name and type and need to route traffic to multiple resources. Additionally, it allows you to associate a Route 53 health check with your records, ensuring that clients receive only reachable DNS responses.
How it Works:
When a client makes a DNS request using Multivalue Answer Routing, AWS Route 53 responds with up to eight healthy records selected randomly from those associated with the domain name. Each of these records can be linked to a Route 53 health check, reducing the chances of clients receiving unreachable DNS responses.
Example:
Suppose you have a domain, “www.example.com,” and you want to distribute traffic across multiple IP addresses. In this case, you might have several A Records with different values:
- www.example.com A Record 192.0.2.2 60
- www.example.com A Record 198.51.100.2 60
- www.example.com A Record 203.0.113.2 60
With Multivalue Answer Routing, Route 53 will respond to DNS queries with up to eight healthy records, helping to avoid downtime if one of the resources becomes unavailable.
Key Considerations:
- Multivalue Answer Routing should not be confused with Elastic Load Balancing (ELB). Route 53 randomly selects any eight records, providing some level of load balancing. However, this is performed by your operating system for cached responses, not by Route 53.
- When creating a Multivalue Answer Record Set with multiple values, each value must be entered separately, usually by creating new resource records with the same name.
- Be cautious when specifying TTL values for multiple records with the same name and type in Multivalue Answer Routing. Route 53 will set the TTL value to the last specified value for all the records.
In summary, the choice between Simple Routing and Multivalue Answer Routing in AWS Route 53 depends on your specific DNS requirements. Simple Routing is suitable for basic scenarios, while Multivalue Answer Routing offers greater flexibility and health check integration for more complex setups. Understanding these policies will help you make informed decisions when managing your DNS traffic on AWS Route 53.