The principles and configuration methods of intelligent DNS resolution (including FAQs)

　　Many people, when configuring domain name resolution, mistakenly believe that "pointing the domain name to an IP address is enough." It's only when they discover that while users on China Telecom access websites quickly, those on China Unicom experience severe lag that they realize domain name resolution is far more complex than simply "pointing" the domain. Intelligent DNS resolution was created precisely to solve the problem of "significant differences in access speeds for users from different sources."

　　I. From Traditional DNS to Intelligent DNS: A Cognitive Upgrade

　　Traditional DNS resolution works simply: regardless of where the user accesses the site, the DNS server returns the same IP address. If your business server is located in a China Telecom data center, China Unicom users will have to transmit data across different carriers, causing latency to spike from 30ms to over 100ms.

　　Intelligent DNS resolution changes this logic of "giving the same answer no matter who accesses it." It dynamically returns the optimal server IP address based on the user's geographical location and network conditions. For example, if the domain example.com is deployed in data centers of China Telecom, China Unicom, and China Mobile, intelligent DNS will ensure that China Telecom users access the China Telecom IP, China Unicom users access the China Unicom IP, and China Mobile users access the China Mobile IP, each using its own "dedicated channel."

　　II. How Smart DNS Works: How Does It "Recognize" Users?

　　The core capability of Smart DNS is identifying the user's origin. However, there's a detail that's easily misunderstood: the authoritative DNS server doesn't see the user's local IP address, but rather the exit IP address of the user's configured LocalDNS (local recursive DNS).

　　Cloud DNS determines the visitor's geographical location by identifying the exit IP address of the LocalDNS, specifically in three scenarios:

　　First: LocalDNS supports EDNS (optimal case). When LocalDNS supports the EDNS Client Subnet (ECS) protocol, it includes the user's real IP subnet information (accurate to the /24 subnet) in its queries to the authoritative DNS. Smart DNS prioritizes reading the IP address from the ECS extended field to determine the user's location, achieving city-level accuracy.

　　Second: LocalDNS doesn't support EDNS (second best). In this case, Smart DNS can only approximate the user's location using the exit IP address of the LocalDNS. If the LocalDNS's exit IP and the user's actual location are within the same provincial administrative region, it still has some reference value; however, if the user uses a public DNS (such as 8.8.8.8), the exit IP may be located in a different region, leading to location inaccuracies.

　　The third type: LocalDNS indirectly supports EDNS. In some network architectures, LocalDNS forwards requests to secondary DNS nodes, which then query the authoritative DNS. In this case, the intelligent DNS sees the exit IP of the secondary node, resulting in lower location accuracy.

　　After determining the user's origin, the intelligent DNS makes scheduling decisions based on three information dimensions: IP geolocation database (determining the location and ISP type), real-time network quality awareness (monitoring latency and packet loss rates between each node and the user's region), and node health status and load (automatically removing faulty nodes).

　　III. How to Configure Intelligent DNS Resolution

　　The core idea of ​​configuring intelligent DNS resolution is to configure different IP addresses for different resolution sources (lines). The following is the standard operating procedure; the console interface of different cloud service providers may vary slightly, but the basic logic is the same.

　　Step 1: Add the domain name. Log in to the console of the intelligent DNS resolution service platform and add the domain name you need to configure to the domain name list. Some platforms require you to modify the NS record of the domain name to the DNS server address provided by the platform before the platform can take over the resolution authority.

　　Step 2: Access Resolution Settings. Click on the target domain name to enter the DNS record management page. Here you can see all the existing DNS records under this domain name.

　　Step 3: Add Multi-Line DNS Records. Click "Add Record" and configure the intelligent resolution rules. Taking an A record as an example, fill in the host record (e.g., www represents a second-level domain, @ represents the domain name itself), select A as the record type, and then add record values ​​for different lines:

　　Resolution Request Source: China Telecom → Record Value: Server IP of China Telecom's data center

　　Resolution Request Source: China Mobile → Record Value: Server IP of China Mobile's data center

　　Resolution Request Source: China Unicom → Record Value: Server IP of China Unicom's data center

　　Resolution Request Source: Default → Record Value: A general IP (as a fallback)

　　Line Priority Rules: The more granular the line, the higher the priority. For example, "Beijing" > "North China" > "China Region"; Custom Line > Search Engine > Cloud Provider > Carrier > Region > Default. The "Default" line has the lowest priority and is used as a fallback for DNS resolution. It is strongly recommended to configure a "Default" line to avoid resolution failures due to some requests not finding a matching line record.

　　Step 4: Set the TTL value. TTL is the cache time of DNS records on LocalDNS, typically 600 seconds (10 minutes) by default. In scenarios requiring urgent IP switching, the TTL can be lowered to 60 seconds beforehand to speed up resolution; during normal operation, the TTL can be appropriately increased to reduce DNS query volume.

　　Step 5: Verify the configuration. After configuration, you can verify it in the following ways: Use an online DNS lookup tool to query nodes in different regions and with different carriers to see if the returned IPs match the configuration rules; or execute the nslookup or ping command on your local computer to test the IP address resolved by the domain name.

　　IV. Advanced Functionality: Weighted Resolution (Load Balancing)

　　Smart DNS not only supports line-based resolution but also weighted resolution—distributing traffic proportionally when multiple IPs are configured on the same line. Each has its specific function, but they can also be used in combination.

　　Line-based resolution solves the problem of "which server a user should go to"—China Telecom users go to China Telecom nodes, and China Unicom users go to China Unicom nodes. Weighted resolution solves the problem of "how to distribute traffic among multiple servers"—distributing users across different physical servers on the same line according to a set ratio.

　　Typical Scenario: You have deployed two servers, A and B, with different performance levels on a Beijing Telecom line (A's performance is 3 times that of B). You want Beijing Telecom users to access these two servers in a 3:1 ratio. Implementation: First, create the "Beijing Telecom" line using line-based resolution; then add two A records under this line, pointing to the IPs of A and B respectively, and setting their weights to 3 and 1.

　　The Smart DNS system randomly returns one of the IPs according to the weight ratio when responding—distributing traffic to each server according to the configured ratio, achieving a weighted round-robin load balancing effect.

　　V. FAQs

　　Q1: Can Smart DNS obtain my real IP address?

　　A1: No. If LocalDNS supports ECS, the authoritative DNS can only obtain the user's IP subnet information (accurate to /24 subnet), not the complete IP address. If ECS is not supported, the authoritative DNS only sees the exit IP address of LocalDNS. The user's local IP address is not directly exposed to the authoritative DNS.

　　Q2: Will using public DNS affect Smart DNS's judgment?

　　A2: Yes. The entry IP address of Google Public DNS may be located around the world. If it does not enable ECS or does not carry the user's subnet information, Smart DNS may locate the user based on the location of Google's PoP node, rather than the user's actual location. For services requiring precise location, it is recommended to use LocalDNS instead of public DNS.

　　Q3: How long does it take for Smart DNS configuration to take effect?

　　A3: After submitting the configuration, it usually takes effect across the entire network within 10-30 minutes, depending on the cache refresh time of LocalDNS in different regions. If the TTL value is lowered beforehand (e.g., 60 seconds), the effect will be faster.

　　Q4: What's the difference between the free and paid versions of Smart DNS?

　　A4: The free version typically only supports the first-level line category (e.g., "North China"), and cannot configure more specific lines (e.g., "Beijing" or "Beijing Telecom"). The paid version (Enterprise Standard/Flagship Edition) supports all specific lines and advanced features such as custom lines and health checks.

　　Q5: Does Smart DNS support overseas lines?

　　A5: Some products do not currently support overseas nodes and lines. If your business targets global users, you need to confirm with the service provider whether they offer overseas line support when purchasing.

　　Q6: Will Smart DNS affect SEO?

　　A6: No. Smart DNS improves access speed, and page loading speed is itself a factor in search engine ranking; therefore, Smart DNS has a positive impact on SEO.

　　In short: Smart DNS resolution identifies the user's origin and returns the optimal server IP for users from different ISPs and regions. The core configuration involves binding the corresponding IP to different lines and setting a default line as a fallback. Route-based parsing solves the "where to go" routing problem, while weight-based parsing solves the "how to distribute traffic" load balancing problem. The two can be used in combination.