Repeated redirects are a highly deceptive type of fault during domain name resolution and website access. Users often see errors like "Page cannot be displayed," "Too many redirects," and "ERR_TOO_MANY_REDIRECTS" in their browsers, while website administrators mistakenly believe it's a problem with the server's redirect rules or SSL configuration. In reality, in many cases, the root cause doesn't originate at the application layer, but rather from CNAME loops or incorrect pointers in the DNS configuration. This causes the resolution process to continuously loop, forming a difficult-to-detect redirect chain.

　　A CNAME record is essentially an alias record. When a domain name is accessed, it automatically resolves to its target domain name, continuing resolution until the final A or AAAA record is obtained. In other words, a CNAME record is merely a pointer relationship and does not generate a real IP address. When one CNAME points to another, the chain continues to extend until the final address is encountered. Normally, this process is simple and fast, but if self-referencing, circular references, or cross-service provider synchronization errors occur in the chain, the resolution process can enter an infinite loop. When a recursive DNS server attempts to resolve a domain name repeatedly, it may give up due to exceeding the hop limit, resulting in access failure.

　　There are many ways to form a CNAME cycle, the most typical being unintentionally pointing two domains to each other. For example, an administrator might want to use a.example.com to point to b.example.com via a CNAME record, while simultaneously configuring b.example.com to point to a.example.com at different times for easier management. When these two records are synchronized with the service provider, a circular link is formed. The query chain will exhibit the following logic:

a.example.com → CNAME b.example.com
b.example.com → CNAME a.example.com

　　From the DNS resolution system's perspective, if 'a' resolves to 'b', and 'b' then resolves back to 'a', the chain cannot be terminated. To avoid an infinite loop, the recursive server will throw an error after several resolution attempts, causing the resolution to fail.

　　Similar loops can also occur in multi-level CNAME structures. For example:

a.example.com → CNAME b.example.com
b.example.com → CNAME c.example.com
c.example.com → CNAME a.example.com

　　This three-node loop is more insidious than a two-node loop, often occurring when multiple service providers are configured together, CDN and DNS are involved in resolution simultaneously, or old records haven't been completely cleaned up during business migration.

　　Besides circular references, improper CNAME configurations can also lead to duplicate redirects. For example, a company might CNAME www.example.com to the main domain example.com, while simultaneously configuring the main domain example.com to CNAME www.example.com. Many sites expect the main domain and the www domain to be compatible by default; however, this kind of "reverse binding" creates a loop at the resolution layer. Typically, the company might have written a forced redirect at the server layer, intending to redirect all access to https://www.example.com, but the combined DNS configuration and server redirection rules ultimately create a loop involving both the DNS and web layers, directly causing access failures.

　　To troubleshoot CNAME loops, the first step is to completely list the resolution paths of all related domains. In a complex environment where a domain name may exist across CDNs, service providers, or multiple regional nodes, simply checking the console of one service provider is far from sufficient. It's essential to observe the actual pointers returned by the recursive DNS. A complete tracing can be performed using tools like `dig` or `nslookup`, for example:

dig www.example.com +trace

　　The output will display the actual records returned by the root server, top-level domain server, and authoritative node level by level. If duplicate pointers or the same CNAME record are repeatedly returned in the DNS resolution path, an anomaly can be basically confirmed.

　　Troubleshooting results usually show two problems: first, the A/AAAA record is ultimately not found in the path; second, the path is terminated by a duplicate CNAME. If there is a prolonged period without a path to an IP address, a loop can be further identified.

　　In multi-vendor configuration scenarios, loops are often caused by "inconsistent record synchronization." For example, a company sets a CNAME record on vendor A, pointing a.example.com to b.example.com; but on vendor B, b.example.com points to a.example.com. If the company adds the NS records for both A and B to the domain name, then the DNS resolution results in different regions will show differences in the path. For example, a record from vendor A might appear normal in one region, while a record from vendor B might appear in a loop in another region. This problem is extremely subtle, often manifesting as access difficulties or intermittent timeouts in certain regions.

　　Besides circular redirects, incorrect CNAME records can also cause repeated redirects. When businesses migrate their operations, they may leave behind CNAME addresses from the old CDN in their DNS records. If accessing that domain results in a 301 redirect via the CDN, combined with internal server redirect settings, this can lead to infinite redirects at the application layer. For example:

user → DNS => old.cdn.example.net → HTTP 301 → new.cdn.example.com → Return 302 → old.cdn.example.net

　　This situation manifests as "too many redirects" in the browser, which is essentially due to a disordered CDN origin zone pointed to by the DNS. The troubleshooting method is to check each CNAME target one by one to ensure it is the latest address, avoiding interference from old records.

　　To address these issues, enterprises can adopt several optimization strategies. First, a key rule must be clear: the main domain should generally not have a CNAME record. The RFC explicitly states that a record with the same name as the main domain example.com cannot simultaneously have a CNAME record with other records, otherwise it will cause a conflict. Many enterprises are accustomed to binding www and the main domain together; this structure should be implemented through web server redirects, rather than through CNAME loops.

　　Second, it is recommended that enterprises simplify the CNAME link as much as possible and avoid crossing multiple service providers. For example:

www.example.com → cdn.example.net → real.cdn.vendor.com → Real Nodes

　　While such a multi-layered structure is usable, it's more prone to looping or redirection errors caused by synchronization delays. The best practice is to point www.example.com directly to the final CNAME provided by the CDN provider, avoiding nested pointers.

　　For multi-service provider primary/backup DNS scenarios, ensure that the authoritative record content of all NS nodes is identical. An automatic synchronization system can be established to automatically synchronize all service providers after each record modification. For example:

records = fetch_primary_dns()
for item in records:
    update_secondary_dns(item)

　　This prevents regions from entering a loop or experiencing incorrect redirects due to inconsistent records.

　　Enterprises should also regularly clean up outdated CNAME records during business migrations. CDN replacements, server migrations, and business splits often leave behind a large number of no longer-used but still existing DNS records. These old records can remain active in certain links, causing multiple redirects. Regularly auditing DNS records and confirming that each pointer is still in use can effectively prevent such hidden failures.

　　Finally, DNS monitoring and intelligent alerts must be enabled. In modern operating environments, DNS resolution failures are often not network-wide but rather regional, gradually spreading, or intermittent. By using global probes to detect CNAME links, recursive query results, redirect counts, and resolution times, anomalies can be detected as soon as a loop forms, and the specific domain name can be quickly located. This is much more efficient than relying on user feedback and reduces access interruptions caused by circular DNS resolution.