Common pitfalls and precautions for multi-line DNS resolution

　　In today's complex domestic and international network environment, more and more website owners are using multi-line DNS resolution, hoping to improve website access speed and stability through intelligent traffic distribution across China Telecom, China Unicom, China Mobile, and even overseas lines. However, in reality, many beginners frequently encounter pitfalls when configuring multi-line DNS, resulting in slow access or even complete website inaccessibility. This article will systematically explain the working principle of multi-line DNS resolution, common misconceptions, and crucial configuration details to help novice website owners avoid pitfalls and truly realize the value of multi-line resolution.

　　I. What is Multi-line DNS Resolution? Why is it Becoming Increasingly Important?

　　Simply put, multi-line DNS resolution returns different server IPs based on the visitor's network operator or region. For example, China Telecom users resolve to China Telecom nodes, China Unicom users to China Unicom nodes, China Mobile users to China Mobile nodes, and overseas users to international lines. The core purpose of this is singular: access from the nearest location + access within the same network.

　　If you only have a single IP address, when a mobile user accesses a China Telecom server, cross-network latency, packet loss, and even speed throttling often occur. Multi-line DNS can effectively alleviate these problems.

　　As website users increasingly access websites nationwide and even globally, multi-line DNS has transitioned from an "optional optimization" to a "basic configuration."

　　II. Common Misconceptions for Beginners: Believing Multi-line DNS Guarantees Speed

　　This is the first and most common pitfall. Many website owners believe that simply enabling multi-line DNS will instantly boost website speed. However, the reality is that multi-line DNS is merely a "scheduling tool." The true determinant of speed is backend resources, including server quality, bandwidth type (shared/dedicated), whether the connection is native, and the interconnectivity of the data center. If your server's network is inherently poor, even the most intelligent DNS will simply distribute users to different "slow nodes."

　　Therefore, the first principle is: multi-line DNS cannot replace a high-quality server; it can only amplify existing advantages.

　　III. Summary of Common Pitfalls with Multi-line DNS

　　1. DNS Shows Support for Multi-line DNS, but It's Not Actually Effective

　　Many DNS service providers advertise support for China Telecom/China Unicom/China Mobile resolution, but this is only in name.

　　Typical Symptoms: All lines ultimately point to the same IP address; mobile users still use the China Telecom exit, and traceroute shows severe cross-network issues.

　　Solution: Test IP resolution using different ISPs. Use an online multi-region DNS testing tool to compare the returned addresses to see if they are truly differentiated. If the lines are not truly separated, it's just "fake multi-line" access.

　　2. Incorrect IP line type, leading to slower access

　　This is a common mistake for beginners. For example, entering BGP IPs into China Telecom/China Unicom/China Mobile lines separately, or configuring a single-line IP to multiple lines simultaneously, results in chaotic scheduling logic, with some users being assigned to the wrong node.

　　The correct approach is: only enter China Telecom lines for China Telecom IPs, only enter China Unicom lines for China Unicom IPs, use BGP IPs as the default line, and configure overseas IPs separately for overseas lines. Ensure that each line corresponds to a "real network".

　　3. Ignoring the importance of the default line

　　Many people only configure the three major ISPs but forget to set the default line. The consequences are: DNS resolution failures for users on the education network, Great Wall Broadband, and China Railcom; abnormal overseas access; and some regions directly returning empty records.

　　The default line is a fallback strategy and must exist. It's generally recommended to use a stable BGP or international line.

　　4. TTL setting too long, causing slow changes to DNS resolution.

　　TTL determines the DNS cache time. A common mistake for beginners is setting it to 600 or 3600 seconds initially, only to find later that the configuration is incorrect and it takes a long time for the changes to take effect.

　　Recommendation: During the debugging phase, set the TTL to 60-120 seconds, and increase it to 300-600 seconds after stabilization. This facilitates troubleshooting without affecting production.

　　5. Neglecting ICP filing and line compliance issues.

　　If your server is located in China and the domain name is not filed, even if the DNS configuration is correct, it may be blocked. Conversely, if the server is overseas but a domestic line is forcibly pointed to an overseas IP, instability is likely to occur.

　　Practical advice: Domestic servers must be filed. Overseas servers should be configured with separate overseas lines; avoid using illegal combinations.

　　IV. Key Details to Consider When Configuring Multi-Line DNS

　　1. Server Lines Must Be Truly Peer-to-Peer: When choosing a server, confirm whether it's a native China Telecom/China Unicom/China Mobile provider, whether it's true BGP (not a pseudo-converged network), and whether it supports dedicated bandwidth. This step determines whether your DNS will truly function effectively later.

　　2. Each Line Must Be Tested: After configuration, don't be complacent. Conduct ping tests, traceroute route analysis, and speed tests from different regions. Only through real-world testing can hidden problems be discovered.

　　3. Website-Level Optimization is Also Necessary: ​​DNS is only the first hop. There are also CDN, web service configuration, image compression, and caching mechanisms. If the server load is too high, even a perfect DNS won't solve the slowness problem.

　　Multi-line DNS is not a "click-and-play" feature, but a systematic project involving server selection, network structure, resolution strategies, and continuous maintenance. For novice website owners, the biggest risk isn't a lack of configuration knowledge, but rather assuming it's already configured correctly.

　　By remembering these three points, you can avoid 80% of the pitfalls:

1. DNS is just for scheduling; the server is the foundation.
2. The network lines must accurately correspond.
3. The default network line must be set.

　　When these fundamentals are in place, multi-line DNS can truly help you improve speed, reduce cross-network latency, and make user access more stable.