Routing Policies – Multi-Value

Routing Policies – Multi-Value Routing

Multi-Value Routing is a DNS-based routing policy used to return multiple healthy records (IP addresses or endpoints) in response to a DNS query. It is a simple way to implement basic load balancing and high availability without a separate load balancer.

 The concept of Multi-Value Routing

In Multi-Value Routing, the DNS server returns multiple values (e.g., A or AAAA records) when queried. Each of these values typically corresponds to a different instance of your application (in different Availability Zones, regions, or servers).

If health checks are configured, only healthy endpoints will be returned in the response.

 Use Case Example

Imagine a web app running on three EC2 instances behind no load balancer:

• app-server-1 – IP: 192.0.2.1
• app-server-2 – IP: 192.0.2.2
• app-server-3 – IP: 192.0.2.3

When a client resolves www.example.com, the DNS returns all three IPs. The client selects one, usually randomly or based on OS/network stack logic.

 Key Features

Feature	Description
Multiple Records	Returns multiple A/AAAA records.
Health Checks	Can associate Route 53 health checks with each record.
Built-in Load Sharing	Traffic gets distributed across multiple endpoints.
No Load Balancer Needed	Lightweight alternative to ELB/ALB for some scenarios.

 Pros

• Simple & cost-effective: No load balancer required.
• Improves availability: Fails over to healthy endpoints.
• Easy to implement: Straightforward setup in DNS.
• Works globally: All clients can receive multiple endpoints.

 Cons

• Basic traffic distribution: No control over traffic percentage or geography.
• Client-side logic: Depends on client/OS behavior to pick an IP.
• Not true load balancing: It only offers rudimentary distribution.

 How twtech Configures Routing Policies – Multi-Value  in AWS Route 53

1. Create a Record Set for your domain (e.g., www.twtech.com).
2. Select Routing Policy = Multi-value answer routing.
3. Add multiple IPs or endpoint records.
4. (Optional) Attach health checks to each value.
5. Enable “Evaluate target health” if using alias records.

 DNS Response Behavior

• Up to 8 healthy records are returned in response to a DNS query.
• If no health checks are configured, Route 53 returns all records.
• If all health checks fail, Route 53 still returns all records (to avoid full outage due to false negatives).

 Example DNS Response (A record)

Query to: api.twtech.com

# json 

{

  "Answers": [

    {"IP": "192.0.2.1"},

    {"IP": "192.0.2.2"},

    {"IP": "192.0.2.3"}

  ]

}

 When to Use Multi-Value Routing

Use it when:

• You want simple DNS-based failover and basic load distribution.
• You're not using a load balancer but want to distribute traffic.
• You need a cost-efficient way to improve resilience.
• You want to improve DNS-level redundancy.

Project: Hands-on

How twtech creates and use the multi-value routing policy for it traffic to resources:

Select the hosted zone to create the record on: twtech.click

Create a record: multi-valuepolicy.twtech.click

Verify that the multi-value policy is working seamlessly from the url on the browser: multi-valuepolicy.twtech.click

From:

To:

Refresh page:

From CloudShell:

Install packages to use the dig and nslookup commands: sudo yum install bind-utils -y

Lets lookup and dig into the multi-valuepolicy record created: nslookup multi-valuepolicy.twtech.click

dig multi-valuepolicy.twtech.click

twtech-insights:

The dig dig and nslookup commands reveals that all the three resoures in all the regions are reachable.