Traditional DNS resolution does not identify the source of a visitor. Instead, it randomly returns one of the available IP addresses. In contrast, smart DNS resolution identifies a visitor's source and returns different IP addresses to different visitors. This ensures that visitors are directed to a specific IP address when they access your website, which reduces DNS resolution latency and improves website access speed.
Function Introduction
For example, assume that the domain name www.cloud-example.com resolves to three IP addresses: one for China Unicom, one for China Mobile, and one for China Telecom. You can use smart DNS resolution to enable proximity-based resolution for visitors from these ISPs.
Intelligent Parsing | Traditional DNS Resolution | |
Parsing Configuration |
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Resolution Result | Alibaba Cloud DNS identifies the visitor’s source:
| Traditional DNS resolution does not identify the visitor’s source: It returns all three IP addresses—192.x.x.1, 192.x.x.2, and 192.x.x.3—to the visitor’s local DNS resolver. The resolver then randomly or preferentially selects one IP address to return to the visitor. This may cause cross-carrier access. |
How It Works
Alibaba Cloud DNS identifies the source of a visitor by detecting the egress IP address of the local DNS resolver, not the IP address of the visitor's device. This process falls into the following three scenarios:
Local DNS Supports EDNS
Because Alibaba Cloud DNS supports the edns-client-subnet extension, it first checks for an IP address within this extension. If an IP address is found, Alibaba Cloud DNS uses that IP address to determine the visitor's geographic location. If no IP address is found, Alibaba Cloud DNS uses the egress IP address of the local DNS resolver.
Local DNS Does Not Support EDNS
The local DNS resolver sends iterative queries to Alibaba Cloud DNS. Alibaba Cloud DNS then uses the egress IP address of the resolver to determine the visitor's location and perform smart resolution.
Local DNS Indirectly Supports EDNS
A user enters example.com in a web browser, which sends a query to the local DNS resolver. The resolver forwards the request to a secondary node, which then queries Alibaba Cloud DNS. In this case, Alibaba Cloud DNS returns resolution results based on the geographic location of the secondary node of the local DNS resolver.
Supported Lines
Lines are organized into a multi-level classification system. You can configure smart resolution rules based on top-level categories or their child classes.
Line | Level 1 Category | Level 2 Category | Level 3 Category |
Region | China, Overseas | Northeast China, North China, Asia, Europe, etc. | Beijing |
carrier | China Mobile, China Unicom, etc. | Northeast China, North China, etc. | Beijing |
Cloud Provider | Alibaba Cloud | China, Overseas | Northeast China, North China, etc. |
Search Engine | Google, Bing | China, Overseas | - |
Custom | Custom classification | - | - |
For detailed descriptions of the lines, see Line Enumeration.
Priority
Line priority is as follows: Custom > Search Engine > Cloud Provider > ISP > Region > Default.
Within each line category, more specific lines have higher priority. For example, Beijing has a higher priority than North China, and North China has a higher priority than China.
The Default line has the lowest priority and is used as a fallback. You must set at least one DNS record for the Default line to prevent resolution failures when no other matching record is found.
Pricing
The smart DNS resolution feature is free of charge. However, the available lines vary based on your subscription edition.
Enterprise Standard Edition and Enterprise Ultimate Edition: All lines are available. To purchase an edition, see Purchase and Attach Domain Names.
Free Edition: Only the top-level categories of certain lines are available, such as Level 1 region lines. Other line classifications are not available.
Scenario Configuration
Scenario 1: ISP-Based Smart Resolution
Assume that your domain name www.cloud-example.com resolves to three IP addresses, one for each of the following ISPs: China Telecom, China Unicom, and China Mobile. You want to achieve the following behavior:
If the visitor's ISP is not China Telecom or China Mobile, Alibaba Cloud DNS returns
192.168.0.1.If visitors are from mobile carriers, Alibaba Cloud DNS returns
192.168.0.2.If the visitor's ISP is China Telecom, Alibaba Cloud DNS returns
192.168.0.3.
Go to the Alibaba Cloud DNS - Public Authoritative Zone page. Find the domain that you want to manage and click its name. Then, click the Settings tab.
On the Settings tab, click Add Record.
Add three DNS records as described in the following table:
Host
Type
Parsing the Request Source
Record Value
www
A
China Mobile
192.168.0.2
www
A
China Telecom
192.168.0.3
www
A
Default
192.168.0.1
Scenario 2: Region-Based Smart Resolution
Assume that the domain name test.cloud-example.com has servers with IP addresses in Zhejiang, Guangdong, and Beijing. You want to achieve the following behavior:
If the visitor is not from South China or North China, Alibaba Cloud DNS returns
192.168.0.7.If the visitor is from South China, Alibaba Cloud DNS returns
192.168.0.8.If the visitor is from North China, Alibaba Cloud DNS returns
192.168.0.9.
Procedure
Go to the Alibaba Cloud DNS - Public Authoritative Zone page. Find the domain that you want to manage and click its name. Then, click the Settings tab.
On the Settings tab, click Add Record.
Add three DNS records as specified in the following table.
Host record
Type
Request Source Parsing
Value
www
A
China_South China
192.168.0.8
www
A
China_North China
192.168.0.9
www
A
Default
192.168.0.7