Summary of Route 53 Routing Policies

Introduction to Routing Policies

• Definition: Routing policies in AWS Route 53 help direct how DNS queries are responded to. They do not route traffic like a load balancer but help resolve hostnames into IP addresses or endpoints for client access.
• Purpose: Allows clients to determine the destination for their HTTP queries or other protocols based on DNS responses.

Simple Routing Policy

• Usage: Typically used to route traffic to a single resource but can support multiple values in the same DNS record. If multiple IPs are returned, the client selects one randomly.
• Alias Record: Only one AWS resource can be specified as the target if used with an alias record.
• Health Checks: Cannot be associated with health checks.
• Example: Creating a simple routing policy involves setting a DNS record with one or more IP addresses. The TTL (Time to Live) is set to define how long DNS caching servers should cache the response.

Practical Example

• Scenario: A simple routing policy was created for simple.stephanetheteacher.com, pointing to an instance in ap-southeast-1. The TTL was set to 20 seconds.
• Modification: The DNS record was edited to include multiple IP addresses, demonstrating how DNS responds to various IPs and how client-side selection works.
• Observation: Using the dig command confirmed the DNS response included the expected IP addresses. Refreshing the DNS query after the TTL expired showed the client randomly selecting between the IPs, demonstrating the simple routing policy.

Key Takeaways

• Routing Policies: Essential for directing traffic based on various criteria, including geography, latency, and resource health.
• Simple Routing: Offers a straightforward way to manage DNS responses, suitable for basic distribution of traffic across multiple resources.
• Practical Application: Creating and modifying DNS records under different routing policies can significantly impact traffic management and resource accessibility.