Alibaba Cloud DNS:Configure an access domain

Process overview

Create Access Domain

Before you begin

• Select a billing method. If you use subscription billing, purchase a subscription instance in advance.

• An Access Domain requires a domain name hosted in a Public Zone. Ensure that at least one domain name in the Public Zone has a Available status for its DNS Server IP Address.

Procedure

1. Navigate to the Alibaba Cloud DNS - Global Traffic Manager console and click Create Access Domain.

2. In the dialog box, select a common scenario or Custom Scenario.

   Common scenarios: Health Check Only (monitor and alert without traffic switching), Active-Standby Disaster Recovery (automatic failover to standby), Active-Active Load Balancing (weighted traffic distribution), Single Data Center with Multiple ISP Egresses (ISP-based routing), Active/Standby Data Centers with Multiple ISP Egresses (cross-datacenter failover with ISP routing), and Multiple Active-Active Data Centers with Multiple ISP Egresses (weighted cross-datacenter balancing with ISP routing).

3. Click the Access Domain icon > Basic Configuration.

4. Complete the form.

   Parameter	Description
   Access Domain	Combines a host record and a domain name. Host record: A custom host record, such as gtm. Domain Name: Select a domain hosted in Public Zone whose DNS Server IP Address is Available.
   Billing Method	Valid options: Subscription and Pay-as-you-go.
   Bind Instance	If you use the Subscription billing method, you must bind a pre-purchased GTM instance.
   Record Type	DNS record type for routing to address pools. Supported types: A (IPv4), AAAA (IPv6), and CNAME (Domain Name).
   TTL (Seconds)	How long (in seconds) the ISP's local DNS caches the record for this Access Domain.
   Enabed State	Controls whether the GTM policy is active. Disabled by default. Enable only after you configure address pools, addresses, and load balancing policies. Important Enabling the Access Domain deactivates any existing DNS record of the same type and name in Access Domain. DNS queries then follow the GTM policy.
   Remarks	Custom label to identify the application service for this instance.

5. The new entry appears in the Access Domain configuration list.

Configure an address pool

Add Address Pool

1. On the Access Domain configuration page, click the Access Domain icon > Add Address Pool.

2. Complete the configuration. Parameter details are in 2. Configure an address pool.

Select Address Pool

1. On the Access Domain configuration page, click the Access Domain icon > Select Address Pool.

2. Select existing address pools. Only pools matching the Record Type of the Access Domain are listed.

   In the Address pool list dialog box, select an address pool from the drop-down list. The address pool type is displayed automatically. Click + Add a new row to add more, or Delete to remove one.

Enable, disable, or delete Access Domain

Impact of changes

Change type	Impact
Enable	Verify that the Access Domain is correctly configured and its Service Availability is Available to avoid DNS errors. If a DNS record with the same name and type exists in Public Zone, DNS queries are routed by the GTM policy for load balancing and failover.
Disable/Delete	The domain reverts to Public Zone for DNS resolution. Misconfigured records in Public Zone can cause DNS errors and service interruptions. Proceed with caution. After you disable or delete an Access Domain, DNS queries may still resolve for the Access Domain until ISP DNS caches expire. The propagation delay depends on the TTL and typically takes 10 to 30 minutes.

Procedure

1. On the Access Domain configuration page, click the Access Domain icon > Enabled / Disabled / Delete.

2. Confirm the operation in the dialog box.

Access Domain

Health Status

Normal: All address pools referenced by the Access Domain are available.

Warning: Some address pools of the Access Domain are unavailable. In the Warning state, resolution continues for available pools but stops for unavailable ones.

Abnormal: All address pools referenced by the Access Domain are unavailable.

Service Availability

Service Availability depends on Enabed State and Health Status:

Enabed State	Health Status	Service Availability
Enabled	Normal or Warning	Available
Enabled	Abnormal	Unavailable (Underlying Resolution Being Performed) GTM performs failover resolution to provide a DNS response whenever possible. Important Failover resolution rules: If a line's address pool becomes unavailable, GTM responds from an available address pool on the global default line with the lowest sequence number. If all address pools for all lines are unavailable, GTM returns addresses from the non-empty address pool with the lowest sequence number, using round-robin rotation.
Disabled	Normal or Abnormal	Unavailable