Alibaba Cloud DNS:FAQ about adding DNS records

Pointing a domain name to a website server is called domain name resolution, which lets users access an IP-based service through an easy-to-remember domain name. For more information, see Add a DNS record.

Alibaba Cloud DNS supports the following record types:

For more information, see Add a DNS record.

No. Record types such as A, AAAA, and CNAME map domain names to IP addresses without port information, so api.example.com can resolve only to 1.1.x.x. To access the service, you must specify the port in the client URL, such as http://api.example.com:8080/. If you do not want to display the port in the domain name, you can hide it by setting up an Nginx reverse proxy for HTTPS forwarding and port hiding.

Use URL forwarding

The URL forwarding record type supports forwarding domain name requests to another URL, which can be in the format of domain name + port number. This acts as a reverse proxy but is not covered by an SLA. For a reliable solution, set up an Nginx reverse proxy for HTTPS forwarding and port hiding.

Scenario: You have a domain name cloud-example.com. The service IP address is 1.1.x.x, and the service port is 8888. You have already configured a DNS record, and the service can be accessed at http://demo.cloud-example.com:8888. Or, you have not configured a DNS record, and the service can only be accessed at http://1.1.x.x:8888.

Goal: You want to access the service at http://www.cloud-example.com without the port number appearing in the URL.

Solution:

1. If the service can only be accessed at http://1.1.x.x:8888, you must first configure a DNS record. For more information, see A record.

   Record Type	A
   Host	demo.cloud-example.com
   Record Value	1.1.x.x

   After the DNS record takes effect, you can access the service at http://demo.cloud-example.com:8888.

2. Configure an Implicit URL Forwarding forwarding record. For more information, see URL forwarding.

   Record Type	Implicit URL Forwarding
   Host	www.cloud-example.com
   Record Value	http://demo.cloud-example.com:8888 Note Q: Why not enter http://1.1.x.x:8888 directly as the record value? A: URL forwarding does not support URLs with IP addresses as record values.

   This lets you access the service at http://demo.cloud-example.com:8888 by visiting http://www.cloud-example.com.

Alibaba Cloud DNS resolves domain names to server IP addresses but does not provide website building services. Build a website on an ECS instance.

If your domain name is not registered with Alibaba Cloud, choose the applicable scenario:

• If your domain name is registered with another provider but has no DNS configuration, see Configure DNS for a domain name not registered with Alibaba Cloud.

• If your domain name, registered with either Alibaba Cloud or another provider, is configured for DNS resolution with another provider and you want to migrate it to Alibaba Cloud DNS, see Migrate DNS resolution to Alibaba Cloud DNS.

Choose a method based on your needs:

• URL forwarding

  When to use: Redirecting users from Domain A to Domain B.

  Requirement: The source Domain A must have a valid ICP license, because the forwarding server of Alibaba Cloud is in the Chinese mainland.

• CNAME record

  When to use: Mapping Domain A as an alias for Domain B so that accessing Domain A yields the same content as accessing Domain B.

  Requirement: CNAME handles DNS resolution only. The destination server must accept requests for the source domain and have proper SSL/TLS certificates, security policies, and firewall rules.

Refer to Add a DNS record for instructions on adding CNAME or URL forwarding records.

• Host: The subdomain prefix. Enter @ for the primary domain name. For example, if your domain name is example.com and you want visitors to use www.example.com, enter www as the host.

• Record value: The value depends on the record type. Examples for common types:

  • A record: The record value is an IPv4 address, such as 192.0.2.0.

  • AAAA record: The record value is an IPv6 address, such as 2001:db8::.

  • CNAME record: The record value is a domain name, such as www.example.com.

  • MX record: The record value is the domain name of a mail server, such as mail.example.com. It usually includes a priority value, such as 10 mail.example.com.

  • NS record: The record value is the domain name of an authoritative DNS server, such as ns1.example.com.

  All record types are described in Add a DNS record.

Yes. Weighted round-robin assigns different weights to each IP address, distributing traffic proportionally. This is useful for A/B testing. Configure weights.

Yes. Alibaba Cloud DNS uses a global anycast network to respond from the nearest server, reducing query latency and propagating record changes in seconds.

DDNS binds a frequently changing public IP to a fixed domain name in real time, enabling external access to home or office network devices. Alibaba Cloud DNS does not currently support DDNS.

The default TTL for all record types is 10 minutes (600 seconds). The minimum TTL varies by edition:

• Free Edition/Personal Edition: The minimum TTL is 10 minutes (600 seconds).

• Ultimate Edition: The minimum TTL is 1 second.

To modify the TTL value, see Configure TTL.

Alibaba Cloud DNS does not limit hosted primary domain names. DNS record limits:

• A maximum of 100,000 DNS records can be added for a single primary domain name, including records for all its subdomains.

• For the same host or subdomain on the same resolution line and with the same record type, the Free Edition of DNS allows a maximum of 10 DNS records, while the paid editions allow a maximum of 100 DNS records.

• For explicit/implicit URL forwarding records, the Free Edition supports 2 records, the Personal Edition supports 5 records, and the Enterprise Edition supports 10 records.

The Premium Edition can exceed these limits. Version Comparison.

For information about wildcard DNS support and how it takes effect, see Wildcard DNS.

High invocation volume triggers global throttling. Use a term query to avoid this issue.

IPv6 (Internet Protocol Version 6) is the next-generation protocol designed to replace IPv4. It solves IPv4 address exhaustion and enables more devices to connect to the Internet.

Alibaba Cloud DNS supports IPv6. Add an AAAA record to enable IPv6 access. The Alibaba Cloud DNS server cluster also fully supports IPv6.

Add a DNS record.

Yes. Multiple IP addresses distribute queries across servers to reduce load. Alibaba Cloud DNS returns all configured addresses to the local DNS, which selects one for the visitor. Weight-based distribution is available through Configure weights.

Yes. Multiple domain names or subdomains can all point to the same IP address:

• Configure multiple websites on an Nginx server

• Configure multiple websites on an IIS server

No. Any public or internal IP address is valid, though internal addresses are typically used only for testing.

Yes. Alibaba Cloud DNS does not restrict IP addresses by geographic location.

DNS returns an IPv6 address only if the client supports the IPv6 protocol stack.

1. Example DNS record configuration:

Resolution effect:

• Dual-stack client (IPv6 + IPv4): The client queries local DNS for both addresses. Alibaba Cloud DNS returns both. The client typically prefers IPv6.

• IPv6-only client: Local DNS queries Alibaba Cloud DNS for the AAAA record and returns the IPv6 address.

• IPv4-only client: Local DNS queries Alibaba Cloud DNS for the A record and returns 1.1.x.x.

2. Example DNS record configuration:

• Dual-stack client, outside the Chinese mainland: The client queries for both IPv6 and IPv4. Alibaba Cloud DNS returns both addresses. The client typically prefers IPv6.

• IPv4-only client, outside the Chinese mainland: No IPv4 address is configured for the "Outside China" line, so resolution fails.

• IPv4-only client, Chinese mainland: Alibaba Cloud DNS returns 1.1.x.x from the default line.

• Dual-stack client, Chinese mainland: Only an IPv4 address is configured for the default line (no IPv6), so Alibaba Cloud DNS returns 1.1.x.x only.

Yes. Weighted round-robin distributes traffic across IP addresses in custom proportions. Set equal weights (1:1) for load balancing. Configure weights.

1. Use addDomainRecord to add a DNS record. By default, A records use the polling mode.

2. Use SetDNSSLBStatus to enable or disable weighted round-robin. Set Open=true to enable weighted round-robin for A or AAAA records.

3. Obtain the RecordId of the DNS record and call UpdateDNSSLBWeight to modify the weight of the record.

   1. If you just added the DNS record in the first step, you can retrieve the RecordId from the return value.

   2. If the DNS record already exists, you can call DescribeDomainRecords to query the RecordId from the list of DNS records.

A CNAME record maps one domain name (alias) to another. URL forwarding redirects requests to a different URL, either implicitly (iframe) or explicitly (301/302 redirect). Key differences:

• A CNAME record preserves the original URL in the address bar; explicit URL forwarding changes it.

• CNAME is best for permanent domain mapping. URL forwarding suits temporary redirects, website migration, or hiding the actual address.

A and CNAME records cannot coexist for the same host and request source line. Use different hosts or request source lines. Other conflict types are listed in DNS record conflict rules.

Different record types have different priorities, so some cannot coexist for the same host and resolution line. Conflicts can cause service unavailability. DNS record conflict rules.

No. CNAME records are designed to map one domain name to another, not to a specific file path or directory.

No. The dot at the end of a domain name represents the root domain. Alibaba Cloud DNS automatically adds it on the backend, so you do not need to add it.

Most large websites, including Baidu, block external CNAME records for security reasons. Use URL redirection (301 or 302) instead.

Yes. Multiple CNAME records are returned based on their weights. Configure weights.

Certain Alibaba Cloud products add a TXT record for domain ownership verification. For example, selecting Automatic DNS Validation for the Domain Validation Method on the SSL Certificates page adds a TXT record automatically. How do I select a domain validation method?

When adding a record for automatic DNS validation, the system removes duplicate or conflicting records from your DNS service.

Priority matters only with multiple MX records. The sending server delivers to the lowest-priority-number server first, then fails over to the next, continuing until delivery succeeds or all servers fail.

Yes. Configure mailbox resolution.

Different record types have different priorities, so some cannot coexist for the same host and resolution line. Conflicts can cause service unavailability. DNS record conflict rules.

Choose the scenario that matches your setup:

• The domain name is registered with Alibaba Cloud, uses Alibaba Cloud DNS, and uses a non-Alibaba Cloud mailbox product.

  Get the required DNS records from your mailbox provider. Configure mailbox resolution.

• The domain name is registered with Alibaba Cloud, does not use Alibaba Cloud DNS, and uses a non-Alibaba Cloud mailbox product.

  Get the required DNS records from your mailbox provider, then contact your DNS provider to add them.

• The domain name is not registered with Alibaba Cloud, uses Alibaba Cloud DNS, and uses a non-Alibaba Cloud mailbox product.

  Get the required DNS records from your mailbox provider. Configure mailbox resolution.

The 'NS record conflicts with subdomain' error usually occurs because multiple different types of DNS records exist at the same level. You can resolve this by carefully checking the existing DNS records, deleting the conflicting ones, and then adding the NS record. However, this operation may affect the resolution of other DNS records under the subdomain. For more information, see DNS record conflict rules.

301 (Permanently Moved): The old URL is permanently replaced. Search engines index the new URL and drop the old one.

302 (Temporarily Moved): The old URL remains valid. Search engines index new content but keep the old URL.

Both codes redirect the browser to a new URL specified in the response Location header.

Choose 301 for permanent moves and 302 for temporary redirects.

URL forwarding records automatically create an underlying A record pointing to Alibaba Cloud DNS forwarding servers. A `dig` result showing an IP address like 203.107.XX.XX instead of your configured URL is normal.

• If prompted that an ICP filing is required, verify that both the source and target domain names have valid ICP filings.

• If a previously working URL forwarding record returns 502, the ICP filing may have become invalid.

URL forwarding routes through Alibaba Cloud servers in the Chinese mainland, so the source domain must have a valid ICP filing. The filing does not have to be through Alibaba Cloud.

You can see an error message in your browser, such as Chrome:

Refused to display 'http://www.example.com/home.html' in a frame because it set 'X-Frame-Options' to 'sameorigin'.

This is because the X-Frame-Options header is set on the target site, which prevents it from being nested in a frame. Contact your website technician to remove the X-Frame-Options configuration from the target site.

Check the JavaScript code on the target URL page. If you find the following code snippet, remove it.

<script>
    if(window.top!=window.self){window.top.location=window.location};
</script>

This usually happens if the target page (the site at the forwarded URL) contains JavaScript code that sets up a redirect. Contact your website technician to investigate.

If a `dig` command for the source domain name does not return an IP address related to 203.107.XX.XX, submit a ticket for Alibaba Cloud DNS, and our technical staff will handle it for you.

This usually occurs during a CC attack when high QPS triggers the forwarding server to stop service. Use an alternative forwarding method.

Symptom: No interception information is displayed in the console.

Cause: The connection is blocked by a same-origin policy. Check the network path for the header of the last 200 OK response. It may contain a same-origin restriction.

Solution: This issue is usually caused by the security policy settings of your website. We recommend that you check your configuration or use only explicit URL forwarding.

The number of supported URL forwarding records varies by Alibaba Cloud DNS edition:

• Free Edition: 2

• Personal Edition: 5

• Ultimate Edition: 10

• Premium Edition: Unlimited

Edition-specific limits are listed under URL Forwarding (Single Domain) in Version Comparison.

The source domain supports HTTP only; the target supports both HTTP and HTTPS. Native HTTPS forwarding is not supported due to certificate management and security constraints. To forward HTTPS requests, configure an HTTPS redirect on your source server. Example Nginx configuration:

server {    
  listen 443 ssl;    
  server_name yourdomain.com;    
  ssl_certificate     /path/to/cert.pem;    
  ssl_certificate_key /path/to/cert.key;    
  return 301 https://targetsite.com$request_uri;
}

Explicit and implicit URL forwarding do not support configuration with parameters.