Alibaba Cloud DNS:FAQ

Can multiple business domain names share the same GTM instance?

It depends on your service scenario.

If your business domain names are mapped to the same group of IP addresses, you can configure canonical name (CNAME) records to point these domain names to the access domain name of the same GTM instance. Otherwise, you must purchase a GTM instance for each business domain name.

Scenario in which the same GTM instance can be shared

The business domain name www.cloud-example.com is mapped to the IP addresses 1.1.XX.XX and 2.2.XX.XX, and disaster recovery is required between the two IP addresses.

The business domain name test.cloud-example.com is mapped to the IP addresses 1.1.XX.XX and 2.2.XX.XX, and disaster recovery is required between the two IP addresses.

In this scenario, two business domain names are mapped to the same group of IP addresses. Therefore, you need to purchase only one GTM instance. You need to only configure a CNAME record for each of the business domain names www.cloud-example.com and test.cloud-example.com by specifying an access domain name in GTM as the record value.

Scenario in which the same GTM instance cannot be shared

The business domain name www.cloud-example.com is mapped to the IP addresses 1.1.XX.XX and 2.2.XX.XX, and disaster recovery is required between the two IP addresses.

The business domain name test.cloud-example.com is mapped to the IP addresses 1.1.XX.XX and 3.3.XX.XX, and disaster recovery is required between the two IP addresses.

In this scenario, two business domain names are mapped to different IP addresses. Therefore, you need to purchase a GTM instance for each of the two business domain names.

What are the differences between GTM and SLB?

GTM uses the Domain Name System (DNS) service to resolve a domain name to multiple IP addresses. This way, different users can access different IP addresses. This allows GTM to balance the access traffic of an application service across multiple IP addresses. GTM checks the health status of IP addresses for DNS resolution and dynamically updates the list of IP addresses that can be returned for DNS requests. This allows the system to implement fault isolation and failovers. Users use the IP addresses returned by GTM to access the corresponding application service and service access traffic does not flow through GTM. Server Load Balancer (SLB) serves as a proxy to distribute user access requests to different servers in real time. Service access traffic of users must flow through SLB.

In most cases, you can use SLB to balance loads across multiple IP addresses that reside in the same region. If you need to balance loads across multiple SLB addresses that reside in different regions, use GTM.

The following table describes the differences.

What are the differences between GTM and Alibaba Cloud DNS?

GTM integrates the intelligent resolution feature of Alibaba Cloud DNS and the application service monitoring feature of CloudMonitor. Therefore, GTM can check the health status of application services, support automatic failovers, and allow users of different Internet service providers (ISPs) or from different regions to access nearby application servers.

Can I use a URL to visit the access domain name in GTM to which a CNAME record points?

No, an access domain name in GTM cannot be directly used as an access URL. An access domain name provided by GTM is the same as a canonical name (CNAME) provided by Alibaba Cloud CDN and other products. It can only be used for service access mapping.

How does GTM determine whether an application service is faulty?

GTM integrates the application service monitoring feature and provides multiple monitoring nodes around the world. You can analyze alerts of multiple monitoring nodes to determine whether an application service is faulty. You can choose to use ping-based health checks, TCP health checks, and HTTP or HTTPS health checks to monitor your application services.

• Ping-based health checks: You can determine whether an application service is faulty based on the packet loss rate or response time.

• TCP health checks: You can determine whether an application service is faulty based on the response time over a port.

• HTTP or HTTPS health checks: You can determine whether an application service is faulty based on the response time and return code information.

How long does GTM take to complete failure recovery?

GTM has been tested and verified by the test team for many times. If an application service fails, a GTM instance of Ultimate Edition can accurately detect the failure and performs a failover within about 1 minute. The network-wide recovery time is equal to the time required for identifying failures and performing failovers plus the time required for the new configuration to take effect on the entire network.

Can domain names be added to address pools in GTM?

Yes, domain names can be added to address pools. GTM allows you to specify IP addresses or domain names in an address pool. However, an address pool cannot contain both IP addresses and domain names at the same time. When an address pool has multiple domain names, round-robin is performed for these domain names.

Does GTM support intelligent DNS resolution?

Yes, you can use GTM to implement intelligent DNS resolution. GTM integrates the intelligent DNS resolution feature. You can use GTM to perform intelligent DNS resolution for users of ISPs in the Chinese mainland, users in seven regions, and users in six continents as well as users in some specific countries. This allows users of different ISPs or from different regions to access nearby application servers, thereby accelerating network access.

Does GTM support session persistence?

No, GTM does not support the session persistence feature. GTM is an advanced DNS service. GTM routes requests from clients to the related addresses of an application service by using DNS responses. Clients can directly connect to the related IP addresses of an application service without the need to connect to GTM. HTTP traffic between clients and application servers does not flow through GTM. Therefore, GTM does not support the session persistence feature.

Can I use both GTM and Alibaba Cloud CDN for a domain name?

Yes, you can use both GTM and Alibaba Cloud CDN for a domain name. Alibaba Cloud CDN can be used before GTM. For more information, see Implement secure access and high service availability by integrating Alibaba Cloud CDN with GTM.

Can I add a CNAME of a CDN service provider to an address pool of GTM?

Yes, you can add a CNAME of a CDN service provider to an address pool of GTM. However, this setting cannot allow the health check and failover features to achieve the optimal result. In most cases, a CDN service provider has a large number of CDN nodes. Compared with the number of CDN nodes, the number of monitoring nodes of GTM is limited. GTM cannot obtain the accurate health statuses and implement failovers. Therefore, we recommend that you do not perform this operation.