Traditional DNS resolution vs. intelligent DNS resolution: Random IP return vs. Directed return of the optimal IP

　　Many people, when using DNS resolution, mistakenly believe that "pointing a domain name to an IP address is enough," unaware of the difference between traditional DNS and intelligent DNS. It's only when they discover—that users in Beijing can access websites quickly, while users in Guangzhou experience severe lag—that they realize domain name resolution is far more complex than simply "pointing" an IP address. The core difference between traditional DNS and intelligent DNS is that the former returns IPs "randomly," pointing all users to the same or a random set of IPs; the latter returns "targeted," providing different users with their respective optimal IPs.

　　Traditional DNS: Random Returns Regardless of Source

　　Traditional DNS resolution works very directly: when a domain name is configured with multiple IP addresses, the DNS server, upon receiving a query request, returns all available IP addresses to the user's LocalDNS. Traditional DNS doesn't care which IP the user ultimately accesses; it only "passes out the IP list."

　　However, the order of the IP addresses in this "passing out" process often holds a hidden meaning. Most DNS servers, upon receiving a request, will randomly rearrange the order of the IP list before returning it. Because clients typically default to using the first IP address in the list to establish a connection, random sorting distributes traffic across multiple servers, achieving basic load balancing. If the same IP is always placed first, all traffic will flood that server, leaving other servers idle. In addition, some DNS servers perform simple sorting optimizations based on the location of the LocalDNS or link quality.

　　The biggest problem with traditional DNS is that it returns the same list of IPs regardless of whether you are a China Telecom or China Unicom user, or whether you are in Beijing or Guangzhou. A China Telecom user might be randomly assigned an IP address from a China Unicom data center, causing latency to spike from 20ms to over 100ms when data packets are transmitted across carriers.

　　Smart DNS: Identifying the Source and Directing the Return

　　Smart DNS changes the logic of "giving the same answer regardless of who comes in." It determines the source of the visitor and returns different IP addresses to visitors from different sources. Its core principle is: identifying which carrier and region the request comes from, then matching it against preset line rules, and returning the corresponding server IP.

　　Determining "where the user comes from" is a crucial step. Intelligent DNS systems determine a visitor's geographical location and ISP type by identifying the exit IP address of the LocalDNS (Local Recursive DNS). If the LocalDNS supports the EDNS Client Subnet (ECS) protocol, the system will prioritize reading the user's real IP subnet information carried in the ECS extended field, achieving location accuracy down to the city level. If the LocalDNS does not support ECS, it must use the LocalDNS's exit IP address to approximate the user's location.

　　Intelligent DNS's redirection capability directly solves the problem of slow access across ISPs and regions. The intelligent route resolution documentation provides a typical scenario: a domain name is configured with three IP addresses—China Telecom IP, China Unicom IP, and China Mobile IP. Intelligent DNS will determine the visitor's ISP type, returning a China Telecom IP to China Telecom users, a China Unicom IP to China Unicom users, and a China Mobile IP to China Mobile users, each using its own "dedicated channel." Intelligent DNS ensures that users access nodes within the same ISP, avoiding cross-network detours.

　　Core Difference: One is "Random," the other is "Directed"

　　The essential difference between the two lies in their different "decision-making criteria." Traditional DNS makes decisions based on "no basis"—it doesn't determine the source or assess node status, either returning a list of all IPs for the client to choose from, or returning them in a fixed or random order. Smart DNS, on the other hand, makes decisions based on multiple dimensions: the user's origin ISP, geographical location, real-time node load, link quality, and even preset line weighting rules.

　　As a result, traditional DNS cannot avoid cross-ISP access and cross-regional routing; smart DNS can achieve precise scheduling, such as "China Telecom users go through China Telecom, China Unicom users go through China Unicom, and Beijing users go to Beijing nodes," significantly reducing latency. Another important difference is fault detection capability. Traditional DNS cannot detect whether backend servers are down, and user requests may continue to be redirected to nodes that are already down; smart DNS typically integrates a health check mechanism, which can monitor node availability in real time. Once an abnormal node is detected, it is automatically removed from the scheduling pool, achieving failover.

　　In scenarios serving multiple IPs, traditional DNS performs "random return"—indiscriminately, all users share the same IP pool; smart DNS performs "targeted return"—precisely matching the optimal node based on the characteristics of different users.

　　Traditional DNS assigns a random address regardless of the source, while smart DNS identifies the source and directs the best address accordingly. This upgrade in resolution logic, from "random" to "directed," directly determines whether a user's access is "potentially fast" or "definitely fast."