Domain name resolution, as the foundation of network communication, directly determines the speed and stability of website access for users worldwide. However, many enterprises providing cross-regional services often encounter a thorny problem—inconsistent domain name resolution across different locations. This means that users in different regions receive different IP addresses when accessing the same domain name, and in some areas, access may be impossible, resolution may fail, or access latency may be abnormal. This phenomenon not only affects user experience but can also lead to business interruptions or inaccessibility, resulting in significant losses.

　　Common causes of inconsistent domain name resolution:

　　1. Uneven distribution of DNS servers

　　The Domain Name System (DNS) is distributed, with multiple nodes worldwide handling domain name resolution requests. Users in different regions send queries to different DNS servers. If a recursive DNS server in a certain region is unstable, has poor performance, or its cached information differs from that of DNS servers in other regions, inconsistent resolution will occur when users access the website.

　　Furthermore, different ISPs or CDN service providers may use different DNS resolution systems. If the resolution results from these DNS service providers are inconsistent, it can lead to users in different regions receiving different IP addresses, and even differences in access latency.

　　2. DNS Caching Validity and Expiration Time

　　The validity and expiration time of DNS records are determined by the TTL (Time-To-Live) parameter. TTL is the lifespan of a DNS record in the recursive server and client caches. Different DNS servers in different regions have different TTLs, which may result in some regions caching older records while others have been updated to newer ones. Since the DNS server only requests a new resolution result from the authoritative DNS server after the TTL expires, a long TTL setting may cause different DNS resolution results to be encountered in different regions.

　　For example, if a DNS server in a certain region has a long cache time and the cached records in that region are not updated in a timely manner, users in that region will see older IP addresses, leading to inconsistent resolution results.

　　3. DNS Load Balancing and Intelligent Resolution Configuration

　　To improve the speed and stability of cross-regional access, many websites use DNS load balancing technology, especially by configuring multiple server nodes to achieve regional traffic scheduling. Intelligent DNS resolution systems typically return the most suitable server IP address based on the user's IP address, region, network operator, and other information. This location-based DNS resolution technology, while effectively improving the access experience for global users, can lead to inconsistent access if misconfigured. For example, in a multi-server deployment, users in some regions might resolve to heavier servers, while users in other regions might resolve to lighter servers. Even if the content is identical across all servers, the performance of servers accessed from certain regions may be poor, resulting in slower access speeds or complete inaccessibility.

　　4. Different DNS Providers

　　Enterprises may use different DNS providers for domain name resolution, especially when multiple providers offer DNS resolution in different regions. Inconsistencies in synchronization can arise. Some providers are slow to update DNS records, potentially causing some regions to access older records or even fail to resolve to the latest IP address.

　　For example, if an enterprise uses global DNS provider A and local DNS provider B, and provider A updates its records promptly while provider B does not, inconsistencies in cross-regional access will occur.

　　5. DNS Poisoning or Hijacking

　　In certain regions or network environments, DNS queries may be poisoned or hijacked. Malicious attackers or network service providers may modify DNS responses, causing some users to access incorrect IP addresses or be redirected to malicious websites. DNS poisoning is common in cross-border access, especially in politically or legally sensitive regions, and may lead to inaccurate resolution of target addresses, resulting in inconsistent access.

　　Solutions for Inconsistent Access Across Regions:

　　To ensure that users across different regions can access the company website normally and stably, and to avoid DNS resolution inconsistencies, enterprises can adopt the following solutions:

　　1. Use a Globally Distributed DNS Service

　　To solve the problem of inconsistent DNS resolution across different regions, enterprises can consider using a globally distributed DNS service provider. These service providers have nodes around the world and can return the most recent DNS resolution results based on the user's actual location. Well-known globally distributed DNS service providers offer intelligent resolution functions, which can dynamically adjust the resolution results based on factors such as region, ISP, and latency.

　　In addition, businesses can consider outsourcing DNS load balancing and traffic distribution to professional service providers to ensure that users in different regions access the nearest and highest-performing server.

　　2. Adjusting and Optimizing TTL Settings

　　To avoid inconsistencies caused by excessively long DNS cache expiration times, businesses can adjust TTL settings appropriately. Lowering the TTL value allows DNS servers to update resolution records more frequently, preventing cache expiration. However, it's important to note that setting the TTL value too low may increase the frequency of DNS queries, thereby increasing the load on the DNS service.

　　Generally, a TTL setting between 300 seconds (5 minutes) and 86400 seconds (24 hours) is suitable. For services with dynamic IP addresses or scenarios requiring frequent adjustments to resolution records, a shorter TTL can be set, while a longer TTL can be used for more stable records.

　　3. Using Anycast DNS Technology

　　Anycast is a technology based on IP routing protocols that allows the same IP address to be published to DNS servers in multiple geographical locations. When a user initiates a DNS query, the query request is routed to the DNS server node closest to the user. Anycast DNS technology effectively reduces DNS query time across regions, ensuring consistent resolution results for users from different regions.

　　In an Anycast network, DNS query requests are routed to the nearest available node, reducing inconsistencies in resolution caused by geographical differences.

　　4. Ensuring DNS Provider Synchronization and Monitoring

　　For enterprises using multiple DNS providers, ensuring record synchronization across all providers is crucial. To this end, enterprises can implement automatic synchronization mechanisms, ensuring that all providers' records are updated promptly after each DNS record modification. Enterprises can use scripts, APIs, or automated tools for record synchronization, avoiding delays and errors caused by manual updates.

　　Furthermore, enterprises should regularly monitor the resolution status of their DNS providers to detect resolution delays, synchronization problems, or unavailability. Professional DNS monitoring tools, such as Pingdom and DNSstuff, can help enterprises monitor the health of DNS resolution in real time, proactively identifying and resolving issues.

　　5. Eliminating DNS Poisoning and Hijacking

　　To prevent DNS poisoning or hijacking, enterprises can employ DNSSEC technology to ensure the integrity and authenticity of DNS queries. DNSSEC uses digital signature technology to verify DNS responses, ensuring that the response data has not been tampered with and preventing DNS hijacking attacks.

　　In addition, enterprises can also use encrypted DNS query methods to ensure the security and privacy of the DNS query process, reducing the risk of DNS poisoning.

　　The problem of inconsistent domain name resolution across different locations is becoming increasingly common in today's distributed architecture and globalized internet environment. Understanding the underlying reasons and taking timely and appropriate solutions is crucial to ensuring the stability of access for global users and the high availability of websites. By using globally distributed DNS services, adjusting TTL settings, applying Anycast technology, ensuring service provider synchronization, and strengthening DNS security, enterprises can effectively reduce inconsistencies across different locations, improve user experience, and ensure continuous business operations. In this process, proper monitoring and rapid response mechanisms are equally important. Only by systematizing and routinely implementing these optimization methods can enterprises cope with the challenges of an increasingly complex network environment.