多CNAME记录指向同一值：get.mysite.com无法访问求助

Hey there! First off, let's clear up a key point: multiple subdomains pointing to the same target is 100% allowed—that's not the problem here. Let's walk through the most likely issues and how to fix them:

1. DNS Propagation or Caching Delays #

DNS changes don't take effect instantly across the entire internet. Even if www.mysite.com is working, get.mysite.com might still be waiting for propagation, or your local device/ISP's DNS server has cached an old (or non-existent) record for get.mysite.com.

• To check the actual DNS resolution for get.mysite.com, run these commands in your terminal:
  • dig get.mysite.com (Linux/macOS)
  • nslookup get.mysite.com (Windows/Linux/macOS)
    Look at the output to confirm it's pointing to sitebuilder.com. If it's not, double-check that you saved the get.mysite.com record correctly in your DNS provider's dashboard.
• Flush your local DNS cache to rule out local caching:
  • Windows: ipconfig /flushdns
  • macOS: sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder
  • Linux (systemd-resolved): sudo systemd-resolve --flush-caches
• Test from a different network (like your phone's cellular data) to see if get.mysite.com works there—this will tell you if it's an ISP-level cache issue.

2. Incorrect DNS Record Type #

Make sure you're using the right record type for get.mysite.com:

• If sitebuilder.com is an A record (points directly to an IP address), your get.mysite.com should be a CNAME record pointing to sitebuilder.com.
• If you accidentally created an A record for get.mysite.com and entered sitebuilder.com as the value (instead of an IP), that won't work—A records require an IP address, not a domain name.
• Double-check that the record wasn't accidentally set to a different type (like MX, TXT) which would break web traffic.

3. Target Server's Virtual Host Configuration #

Even if DNS is resolving correctly, the server hosting sitebuilder.com might not be configured to accept requests for get.mysite.com. Web servers use virtual hosts to map domain names to content, so if only www.mysite.com is listed:

• For Nginx: Check your server block and ensure server_name includes get.mysite.com (e.g., server_name www.mysite.com get.mysite.com;).
• For Apache: Verify your <VirtualHost> block has ServerAlias get.mysite.com alongside the main ServerName.
• If you're using a site builder platform (like the name suggests), check its domain settings to make sure get.mysite.com is added as an allowed custom domain.

Quick Recap #

Multiple subdomains pointing to the same target is totally valid. Start by verifying DNS resolution with dig/nslookup, then check for caching issues, record type mistakes, and finally the server's virtual host setup.

内容的提问来源于stack exchange，提问作者BaBurger