GTM provides the address pool feature to simplify the address management of application services. The following describes how to use IP address pool configurations and the use cases.
A GTM instance can be configured with multiple address pools. Users in different regions can access the nearest address pool. When an address pool is unavailable, services can be failed over to a backup address pool.
Up to 20 accessible address pools can be added to an instance.
Set an address pool name that is easy to remember and recognize. The name can contain both Chinese and English characters, for example, Telecom address pool 01. In access policies, accessible address pools are distinguished by names.
You can set the type of addresses in an address pool to IP address or domain name.You may use multiple IP addresses to provide the load balancing service to many users. Address pools of the domain name type are provided to suit your services that use CDN addresses or domain names such as Anti-DDoS and firewalls. When an address pool contains multiple domain names, GTM starts the round robin service to distribute traffic to these domain names.
For an address pool with multiple IP addresses, the system monitors the health status of the IP addresses through health check, counts the number of healthy IP addresses in real time, and isolates faulty IP addresses. If the number of healthy IP addresses in the address pool is less than the value of Minimum Available Addresses, the system sets the address pool to Unavailable and the access policy determines whether to switch to the failover address pool based on the address pool status.
When adding IP addresses to an address pool, you can set the IP addresses to different work modes. The default work mode is Smart Return. Supported work modes are described as follows:
- Smart Return: The system blocks IP addresses dynamically based on the health check status. When the health check of an IP address returns normal results, DNS resolution returns the IP address to the user. When an IP address is abnormal, DNS resolution deletes the IP address temporarily.
- Always Online: In this mode, the system regards that the IP address is always normal, DNS resolution returns the IP address to the user invariably, and health check is not performed on the IP address.
- Always Offline: In this mode, the system regards that the IP address is always abnormal, DNS resolution does not return the IP address to the user, and health check is not performed on the IP address. The IP address only exists in system configuration and will be enabled after a period.
After you select Weighted Round Robin for Balancing Policy on the Global Settings page, you can set the weight of an IP address to be added to an address pool. You can set different weights for different IP addresses so that access traffic is distributed to the IP addresses based on their weights.