This topic describes how to implement fault isolation or failover through DNS.
Scenarios
Enterprise websites or applications typically use public zones to configure intelligent DNS resolution, which improves access speed and quality across different Internet Service Providers (ISPs) or regions. For example, the intelligent DNS resolution configuration for the domain dns-example.com is as follows:
Record type | Host record | Query source | Record value | TTL |
A | www | China Unicom | 192.0.x.x | 10 minutes |
A | www | China Mobile | 192.1.x.x | 10 minutes |
A | www | China default | 192.2.x.x | 10 minutes |
The intelligent resolution effects are:
When Unicom users visit the application through domain name, it resolves to the IP address 192.0.x.x.
When Mobile users visit the application through domain name, it resolves to the IP address 192.1.x.x.
When other users visit the application through domain name, it resolves to the default IP address 192.2.x.x.
What impact will it have on users if the Unicom IP address 192.0.x.x becomes unavailable?
Unicom users access the application IP address through the domain name: Access failed.
When Mobile users visit the application through domain name, it resolves to the IP address 192.1.x.x.
When other users visit the application through domain name, it resolves to the default IP address 192.2.x.x.
How can the traffic of China Unicom users be automatically switched to the IP addresses of other ISPs when the IP address of China Unicom is unavailable?
Use authoritative DNS resolution with Global Traffic Manager (GTM) to implement failover. GTM includes a health check feature that monitors IP addresses. Based on the health check results, GTM determines whether an IP address has failed. If a failure is detected, GTM switches the domain name resolution to a backup IP address. This process enables automatic failover. For more information, see Use GTM to implement DNS resolution and failover based on ISP.