Alibaba Cloud DNS:Address pool configuration

What is an address pool?

In Global Traffic Manager (GTM), an address pool groups IP addresses or domain names that provide the same application service and share common properties, such as region or carrier. Configure multiple address pools for a GTM instance to route users to the nearest endpoints for proximity access and enable failover when an address pool collection becomes unavailable.

Parameters

1. Address pool name

   Choose a descriptive, memorable name. Access policies use the pool name to identify the destination for traffic routing.

2. Address pool type

   Supported types include IPv4, IPv6, and domain name.

   Note

   IP addresses are the most common type. Domain name addresses are useful for hostname-identified services such as CDN endpoints, Anti-DDoS instances, or firewall services. Address pools with multiple domain names only support the return addresses by weight policy.

3. Load balancing policy

   GTM supports two policies: return all addresses and return addresses by weight.

   With return addresses by weight, you assign a weight to each IP address in the pool.

   Address weight: Assign a weight to each IP address. GTM returns addresses based on their weights, distributing traffic proportionally. You can set load balancing policies at both the pool level and the individual address level.

   Address pool policy	Address policy	Supported
   return addresses by weight	return addresses by weight	Yes
   return all addresses	return addresses by weight	Not supported. The address-level "return addresses by weight" policy is ignored, and the "return all addresses" policy of the address pool takes precedence.
   return all addresses	return all addresses	Yes
   return addresses by weight	return all addresses	Not supported. The address-level "return all addresses" policy is ignored, and the "return addresses by weight" policy of the address pool takes precedence.

   Note

   You cannot configure load balancing policies for latency-based access policies.

   Weight calculation rules

   When both the pool-level and address-level policies use return addresses by weight, the final weight is calculated as: Final address weight = Address pool weight × Address weight.

   1. Example 1: With the weights below, the final weight for 1.1.1.*1 is 2 × 4 = 8.

   Address pool	PoolA	PoolB
   Address pool weight	4	2
   Address	1.1.1.*1	2.2.2.*2
   Address weight	2	3

   2. Example 2: If address 1.1.XX.XX exists in both PoolA and PoolB, its total weight is the sum from each pool: (2 × 4) + (1 × 1) = 9.

   Address pool	PoolA		PoolB
   Address pool weight	4		1
   Address	1.1.XX.XX	2.2.XX.XX	1.1.XX.XX	3.3.XX.XX
   Address weight	2	3	1	3

4. Address

   Enter the application service address. For IP type pools, enter the IP address. For domain name type pools, enter the domain name.

5. Address region correction

   Specifies the geographic location of the address. GTM auto-detects the location when you enter an address. Click Correction to override the detected location.

   Note

   For domain name type address pools, you must manually specify the geographic region.

   In the Select Address Region dialog box, select a region from the three-level panel. First-level categories: carrier, Chinese mainland, Regions outside the Chinese mainland, Alibaba Cloud, and Do not correct. Under carrier, select China Telecom, China Unicom, or China Mobile, then select specific regions at the third level. The panel supports search.

6. Address working mode

   Set one of the following working modes for each IP address:

• Smart return: Default mode. DNS returns healthy IP addresses and temporarily removes unhealthy ones based on health check results.

• Always online: DNS always returns this IP address regardless of health status. Health checks still monitor and send alerts but do not remove, add, or fail over the IP address.

• Always offline: DNS never returns this IP address. The address remains in the configuration for future use. Health checks still monitor and send alerts but do not remove, add, or fail over the IP address.

7. Add a single entry and add entries in bulk

   Add addresses one by one or in bulk.

Address pool operations

1. Add address pool

   Create a new address pool with the name, type, load balancing policy, addresses, region correction, and working mode.

   Note

   • You can add up to 10 access address pools to a Standard Edition instance.

   • You can add up to 20 access address pools to an Ultimate Edition instance.

2. Modify

   Edit the name, type, load balancing policy, addresses, region correction, or working mode of an existing address pool.

3. Delete

   Delete an address pool. You must first remove any associated access policies.

4. Health check

   When enabled, health checks monitor application service availability in real time using PING, TCP, or HTTP(s). Enable health checks.

Procedure

1. Log on to Alibaba Cloud DNS-Global Traffic Manager.

2. On the GTM instance list, click the target instance. On the global configuration page, click the Address Pool Configuration tab, then click Add Address Pool.

3. In the Add Address Pool dialog box, enter the address pool name, address pool type, load balancing policy, address, address region, address weight, and address working mode. Then, click Confirm.

4. After you add the address pool, its configuration appears on the Address Pool Configuration page.

   The Address Pool Configuration page lists all address pools with their names, policies, and types. It supports Modify and Delete operations. Expand a pool to view details such as Address Pool ID, Creation Time, Health Check status, and the address list with each address's Address Region, Mode, and Health Check Status.

Feature Rules

1. Maximum address pools per instance: 10 (Standard Edition), 20 (Ultimate Edition).

2. Maximum addresses per pool: 20 (IP addresses or domain names).

3. Address pool weights require the return addresses by weight policy in the address pool collection.

4. Without health checks, pool availability depends on address working mode: Smart return or Always online indicates normal; Always offline indicates abnormal.

5. To delete a pool used by an access policy, remove or modify the access policy first.