Alibaba Cloud DNS:FAQ about features of Alibaba Cloud DNS

1. Does Alibaba Cloud DNS limit the number of domain names and DNS records to be added?

Alibaba Cloud DNS does not limit the number of domain names to be added. For the same resolution line, the free edition supports a maximum of 10 DNS records and each paid edition supports a maximum of 90 DNS records.

2. How do I import DNS records to Alibaba Cloud DNS?

For more information about how to import DNS records to Alibaba Cloud DNS, see Import DNS records.

3. What types of DNS records does Alibaba Cloud DNS support?

Alibaba Cloud DNS supports the following types of DNS records: A, AAA, CNAME, MX, TXT, NS, SRV, and CAA. In addition, Alibaba Cloud DNS supports implicit URL forwarding records and explicit URL forwarding records. For more information, see Add a DNS record.

4. Does Alibaba Cloud DNS support IPv6 addresses?

You can add AAAA records in Alibaba Cloud DNS to point domain names to IPv6 addresses. In Alibaba Cloud DNS, DNS servers also support IPv6 addresses.

5. Does Alibaba Cloud DNS support wildcard DNS records?

Yes, Alibaba Cloud DNS supports wildcard DNS records. When you add a DNS record, you can use the asterisk (*) as a wildcard to point all subdomain names of a domain name to the same record value. This is also known as wildcard DNS. For example, you can add a DNS record for the domain name *.example.com. This way, all subdomain names of *.example.com such as www.example.com and subdomain.example.com can be matched in DNS queries. Alibaba Cloud DNS supports wildcard DNS records for all types of DNS records except SRV records and URL forwarding records.

6. What is the TTL period provided by Alibaba Cloud DNS?

A time-to-live (TTL) period is the period of time that a DNS record can be cached on a DNS server. When a DNS server receives a DNS query, the DNS server sends the DNS query to the name servers specified for the requested domain name to obtain resolution results. The DNS server then caches the resolution results as a DNS record for a period of time. If the DNS server receives DNS queries for the same domain name during this period of time, the DNS server directly returns the cached resolution results, instead of sending the DNS queries to the specified name servers to obtain resolution results. The default TTL period is 10 minutes, which equals 600 seconds, in Alibaba Cloud DNS. The TTL period can be changed. The value range of the TTL period varies based on the edition of Alibaba Cloud DNS. For more information, see TTL definition.

7. Can a domain name point to multiple IP addresses?

Yes, you can point a domain name to multiple IP addresses. This way, DNS queries can be evenly distributed to multiple DNS servers to reduce the loads on DNS servers. For example, you can add A records in Alibaba Cloud DNS to map a domain name to multiple IP addresses. When a visitor sends a DNS query for the domain name, Alibaba Cloud DNS returns a list of all the specified IP addresses to the local DNS server of the visitor. Then, the local DNS server determines to return which IP address to the visitor.

8. How long does it take to synchronize a DNS record modified in Alibaba Cloud DNS to global DNS nodes?

After you modify a DNS record, Alibaba Cloud DNS can synchronize the modification to DNS nodes around the world within 10 seconds. Take note that your local DNS servers are beyond the control of Alibaba Cloud DNS. DNS records are cached on local DNS servers based on the TTL period that you specify.

9. Does Alibaba Cloud DNS support weighted round-robin?

Yes, Alibaba Cloud DNS supports weighted round-robin. If a domain name is translated into multiple IP addresses, you can use weighted round-robin to set a weight for each IP address. This way, access traffic is forwarded to different IP addresses by weight. During A/B testing, you can use this feature to forward a small portion of traffic to a server on which the software is updated. For example, the domain name www.example.com points to two IP addresses, one of which has a weight of 3 and the other has a weight of 1. In this case, Alibaba Cloud DNS returns the IP address with a weight of 3 for 75% of the time, and the IP address with a weight of 1 for 25% of the time. The weight can be set to a number in the range of 0 to 100. For more information, see Set weights.

10. What is intelligent DNS resolution?

During intelligent DNS resolution, DNS servers return different IP addresses based on the sources of visitors. This enables visitors to obtain the IP addresses specified for the website that they access. For more information about intelligent resolution lines, see Intelligent DNS resolution.

11. How does Alibaba Cloud DNS use intelligent DNS resolution to determine the geographic location of a visitor?

Alibaba Cloud DNS determines the geographic location of a visitor based on the egress IP address of the visitor's local DNS server.

12. How do I configure intelligent DNS resolution?

You can configure intelligent DNS resolution in the Alibaba Cloud DNS console. When you add a DNS record, you must select the geographic location where you want the DNS record to take effect for a resolution line. For example, the geographic location can be a country or region on a continent outside the Chinese mainland. For more information, see Intelligent DNS resolution.

13. How is intelligent DNS resolution charged?

The intelligent DNS resolution feature is not separately charged. The fee for intelligent DNS resolution is included in the fee you pay when you purchase Alibaba Cloud DNS. In addition, the resolution lines supported by Alibaba Cloud DNS vary based on the edition of Alibaba Cloud DNS. For more information, see Pricing and Editions.

14. Does Alibaba Cloud DNS limit the type of IP address for a DNS record value?

Alibaba Cloud DNS does not limit the type of IP address for a DNS record value. When you add a DNS record, you can enter a public IP address or a private IP address as the record value.

15. How do I configure reverse DNS lookup or add a PTR record?

Reverse DNS lookup requires that IP addresses be mapped to domain names. To configure this feature, you must contact the service provider of your data center or DNS server. If your server is provided by Alibaba Cloud, you can submit a ticket. The after-sales support engineers of Alibaba Cloud can help you configure reverse DNS lookup.

16. Does Alibaba Cloud DNS support DNSSEC?

Yes, Alibaba Cloud DNS supports DNSSEC. Domain Name System Security Extensions (DNSSEC) is a DNS authentication mechanism provided by the Internet Engineering Task Force (IETF). DNSSEC enhances DNS authentication by using digital signatures based on public key encryption, and therefore adds security protection to the DNS infrastructure. This feature ensures that visitors are accurately directed to your web servers and also helps you defend against DNS cache poisoning.

17. Does Alibaba Cloud DNS support DDNS?

No, Alibaba Cloud DNS does not support dynamic DNS (DDNS). DDNS is a method of mapping the dynamic IP addresses of visitors to a fixed DNS resolution service. Each time a visitor connects to the network, the client transmits the dynamic IP address of the visitor to the server of the service provider. The server then provides the DNS resolution service to dynamically resolve the domain name.

18. Does Alibaba Cloud DNS support DNS records that point domain names to ports?

This depends on the type of DNS record that you add. When you add an A or AAAA record, Alibaba Cloud DNS does not allow you to enter the record value in the format of Server IP address:Port number to map a domain name to a port. When you add a URL forwarding record, you can enter the record value in the format of Domain name:Port number to map a domain name to a port.

19. Does Alibaba Cloud DNS support DNS resolution for subdomain names?

Yes, Alibaba Cloud DNS supports DNS resolution for subdomain names. For more information, see Subdomain management.

20. Does Alibaba Cloud DNS support anycast?

Yes, Alibaba Cloud DNS supports anycast. Alibaba Cloud DNS responds to the DNS queries of visitors by using the DNS servers that are closest to the geographic locations of visitors through the anycast between the DNS servers around the world. This way, Alibaba Cloud DNS delivers query performance with low latency and synchronizes DNS record changes to DNS nodes around the world within seconds.

21. In which regions are Alibaba Cloud DNS nodes deployed?

The free edition of Alibaba Cloud DNS provides DNS nodes that are deployed in Hangzhou, Shanghai, Shenzhen, and Beijing. The paid editions of Alibaba Cloud DNS provide DNS nodes that are deployed in Zhangjiakou, Beijing, Chengdu, Heyuan, Shanghai, Hangzhou, Shenzhen, Hong Kong (China), Japan, Singapore, Malaysia, India, Indonesia, Australia, Eastern United States, Western United States, Germany, UK, and UAE.

22. Can I use subdomains hosted by Alibaba Cloud DNS if the primary domain is hosted by a third-party DNS service provider?

Yes, you can use subdomains hosted by Alibaba Cloud DNS if the primary domain is hosted by a third-party DNS service provider. For more information about how to add a subdomain name, see Subdomain management.

23. Why is no DNS record displayed for a subdomain name after I add the subdomain name to the authoritative domain name list?

After you add a subdomain name, the DNS records of the corresponding primary domain name must be synchronized to this subdomain name. These operations are performed asynchronously. We recommend that you wait a few minutes and then refresh the page.

24. Why is the DNS server state of a subdomain name displayed as "Running exception" after I add the subdomain name?

This is because Alibaba Cloud DNS does not find the DNS server information about the subdomain name. This state may appear if no DNS server is configured for the subdomain name. If this issue occurs, you can go to the DNS Settings page of the subdomain name and obtain the DNS server names assigned by Alibaba Cloud DNS to the subdomain name. Then, you can add two NS records for the primary domain name to point the subdomain name to each DNS server name assigned by Alibaba Cloud DNS.

Note: After NS records are added for the primary domain name, the DNS server state of the subdomain name may still be displayed as "Running exception" on the DNS Settings page. This is because the DNS server status is detected on a regular basis but not in real time. We recommend that you wait a few minutes and then refresh the page.

25. Is DNS resolution affected if I remove a subdomain name because the subdomain name conflicts with an NS record that I want to add for the corresponding primary domain name?

If an NS record that you want to add for a primary domain name conflicts with a subdomain name, you must remove the subdomain name from the primary domain name and then add the NS record. However, this operation affects the DNS resolution of the subdomain name.

26. Why are the DNS server names assigned by Alibaba Cloud DNS to a subdomain name not displayed on the DNS Settings page after I add the subdomain name?

After you add a subdomain name, Alibaba Cloud DNS assigns DNS server names to the subdomain name. These operations are performed asynchronously. We recommend that you wait a few minutes and refresh the page. Then, you can go to the DNS Settings page of the subdomain name and view the DNS server names assigned by Alibaba Cloud DNS to the subdomain name in the upper part of the page.

27. Can I use subdomains hosted by the free edition of Alibaba Cloud DNS if the primary domain is hosted by a paid edition of Alibaba Cloud DNS?

No, you must make sure that the primary domain and subdomains are hosted by the same edition if they are both hosted by Alibaba Cloud DNS. If the primary domain is hosted by a paid edition of Alibaba Cloud DNS, the subdomains must be hosted by the same paid edition of Alibaba Cloud DNS.

28. Is DNS resolution affected if subdomains are hosted by Alibaba Cloud DNS and I want to change the DNS service provider of the primary domain from a third-party DNS service provider to Alibaba Cloud DNS?

No, DNS resolution is not affected if you perform the following steps to change the DNS service provider of a domain:

(1) If the primary domain name is not registered with Alibaba Cloud, add the primary domain name in Alibaba Cloud DNS. If the primary domain name is registered with Alibaba Cloud, skip this step.

(2) After the primary domain name is added, import its DNS records to Alibaba Cloud DNS and add NS records for the primary domain name to point the subdomain names to Alibaba Cloud DNS.

(3) Change the DNS servers of the primary domain name at the registrar of the primary domain name.

(4) Retain the NS records of the primary domain name at the original DNS service provider for at least 48 hours after the DNS servers are changed.

29. What can I do if an NS record that I want to add under a primary domain name conflicts with existing DNS records when I add a subdomain name?

You can remove the subdomain name from the primary domain name and add the NS record again.

30. What can I do if both the primary domain and subdomains are hosted by Alibaba Cloud DNS and I want to change the DNS service provider of the primary domain to a third-party DNS service provider without affecting DNS resolution?

You can perform the following steps to change the DNS service provider of a domain:

(1) On the website of a third-party DNS service provider, add NS records for the primary domain name to point its subdomain names to Alibaba Cloud DNS.

(2) Change the DNS servers of the primary domain name at the registrar of the primary domain name.

(3) Retain the NS records of the primary domain name in the Alibaba Cloud DNS console for at least 48 hours after the DNS servers are changed.