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应用层 The Application Layer

DNS

  • A record, domain -> IP
  • CNAME record, domain -> domain

The @ symbol is used to represent the root or apex of the domain. This means that when you use @ in DNS records, you are referring directly to your base domain, for example, fenglyulin.com.

When configuring DNS records, here’s how you can use the @ symbol:

  • A Record: Pointing @ in an A record to an IP address means that your base domain (fenglyulin.com) will resolve directly to the specified IP.
  • CNAME Record: Typically, CNAME records are not used with @ because they can cause conflicts with other essential DNS records like SOA and MX. However, some DNS providers offer workarounds that essentially allow a CNAME-like functionality at the apex domain level.
  • MX Record, TXT Record, etc.: Using @ with these records applies them to your entire base domain, affecting how emails are routed or how domain ownership is verified, respectively.

For your case with doc.fenglyulin.com, as you mentioned earlier, you have correctly used a CNAME to point this subdomain to your Vercel app. Just ensure you have also configured everything on the Vercel side to recognize and properly handle requests to doc.fenglyulin.com.

Some commands/websites to check the data

  • dig to iteratively find the next mapping domain one by one
dig doc.fenglyulin.com CNAME
dig fenglyu-docs-site-v1.vercel.app CNAME
  • nslookup to find directly find the
nslookup fenglyu-docs-site-v1.vercel.app
  • dns checker

Problem record

image-20240429220817851

Reference

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