Alibaba Cloud DNS:Get started with Global Traffic Manager 3.0

Solution architecture

Two data centers host the service: a primary data center handles daily traffic, and a backup data center serves as the failover target. If the primary data center becomes unavailable due to network issues or a service interruption, GTM directs traffic to the backup data center.

GTM processes traffic in four stages:

1. Health check -- GTM continuously monitors the service addresses in the Primary-DC and Backup-DC address pools.

2. DNS query -- A user initiates a request. The local DNS sends a query for the service domain name to GTM.

3. Traffic scheduling -- If the primary address pool is healthy, GTM returns its IP address. If the primary pool fails, GTM returns the backup pool's IP address instead.

4. Fault recovery -- After the primary pool recovers, GTM either switches traffic back (Preemptive Mode) or keeps traffic at the backup pool (Non-Preemptive Mode), depending on the configured mode.

Prerequisites

Before you begin, make sure that you have:

• An Access Domain hosted by Public Zone, with at least one DNS Server IP Address in Available status

• Primary and backup services deployed with public IP addresses (for example, Shanghai data center at 121.21.*.* and Hangzhou data center at 139.3.*.*)

Step 1: Create an access domain

1. Go to the Global Traffic Manager console.

2. On the Access Domain tab, click Create Access Domain.

3. In the dialog box, select Custom Scenario.

4. On the Access Domain configuration page, click the access domain name icon and select Basic Configuration.

   

5. Configure the following settings.

   Setting	Value
   Access Domain	Enter an access domain name, for example, gtm.your-domain.com. If the drop-down list is empty, purchase a domain name or go to Public Zone to add a third-party domain name.
   Billing Method	Select Pay-as-you-go.
   Record Type	Select A. This guide uses IPv4 addresses.
   TTL (Seconds)	Keep the default value of 30. A shorter TTL speeds up DNS failover but increases DNS query volume.
   Enabed State	Keep the default disabled status. Enable it after all configurations are complete.
   Remarks	Enter a description.

   

Step 2: Add primary and backup address pools

An address pool is a collection of service addresses. Create one pool for the primary data center and one for the backup.

1. Click the Access Domain icon, and then click Add Address Pool.

   

2. Configure the following settings. For details, see Address pool configuration.

   Setting	Value
   Address Pool Name	Primary-DC
   Type	IPv4
   Health Status Conditions	Select At least one address in the address pool is available. The pool is considered healthy if at least one address passes health checks.
   Enabed State	Enable

   

3. Repeat these steps to create a backup address pool named Backup-DC.

Step 3: Add service addresses

1. Click the icon for the address pool you created, and then click Add Address.

   

2. Configure the following settings. For details, see Address configuration.

   Setting	Value
   Address Name	Primary-Server-01
   Type	IPv4
   Type	Enter the public IP address of the server in the primary data center.
   Health Check	Enable. Configure the probe protocol (such as HTTP or HTTPS), the path (such as /health), and the expected response code. GTM uses this configuration to determine whether the service is available.

   

3. Repeat these steps to add a service address to the Backup-DC address pool. The result looks like the following figure.

   

Step 4: Configure the load balancing policy

GTM applies two layers of traffic scheduling: a policy between address pools and a policy among addresses within each pool. The pool-level policy is applied first, then the address-level policy.

Within an address pool

In this guide, each address pool contains only one service address. Keep the default Round Robin policy.

Step 5: Enable the access domain and verify DNS resolution

A newly configured access domain is disabled by default. After completing all settings, enable it manually.

1. Verify that all health checks are passing. If any red or orange alert indicators appear, troubleshoot the address health checks before proceeding.

2. Click the access domain name icon and select Enable.

   

3. In the confirmation dialog box, review the settings and submit the configuration.

4. Wait approximately 10 minutes for the configuration to take effect.

nslookup gtm.your-domain.com

Server:   <your-local-dns>
Address:  <your-local-dns>#53

Non-authoritative answer:
Name:     gtm.your-domain.com
Address:  121.21.*.*

dig gtm.your-domain.com

;; ANSWER SECTION:
gtm.your-domain.com.  30  IN  A  121.21.*.*

Step 6: Configure a CNAME record for traffic steering

Point your service domain name to the Access Domain by creating a CNAME record. For example: home.example.com CNAME gtm.your-domain.com.

1. Go to the Alibaba Cloud DNS - Public DNS console. Find the target domain name and click Settings.

2. Click Add Record and configure the following settings.

   Setting	Value
   Record Type	CNAME
   Host	Enter the host record for traffic steering.
   Value	Enter the configured access domain name.

   

Billing

For pricing details, see Product Billing.

References

• FAQ

• Best practices