Introduction

WordPress multisite with subdomain configuration requires each subdomain site to resolve to the same server IP address. This is typically achieved with a wildcard DNS A record (*.example.com). When the wildcard record is missing or misconfigured, subdomain sites return DNS resolution errors, making them completely inaccessible to visitors.

Symptoms

  • Subdomain site returns DNS_PROBE_FINISHED_NXDOMAIN in browser
  • dig site1.example.com returns NXDOMAIN
  • Main site works but subdomain sites do not
  • WordPress multisite network admin shows subdomain sites as active but they are unreachable
  • Error message: This site can't be reached. site1.example.com's server IP address could not be found

Common Causes

  • Wildcard DNS A record (*.example.com) not configured at the DNS provider
  • Wildcard record was deleted during DNS maintenance
  • DNS provider does not support wildcard records on the current plan
  • Subdomain-specific A record pointing to the wrong IP address
  • DNS propagation delay after adding the wildcard record

Step-by-Step Fix

  1. 1.Check DNS resolution for the subdomain: Confirm the record is missing.
  2. 2.```bash
  3. 3.dig site1.example.com A +short
  4. 4.# Returns nothing (NXDOMAIN)
  5. 5.dig *.example.com A +short
  6. 6.# Should return the server IP
  7. 7.`
  8. 8.Add a wildcard DNS A record: Point all subdomains to the server IP.
  9. 9.```dns
  10. 10.# At your DNS provider:
  11. 11.# Type: A
  12. 12.# Name: *
  13. 13.# Value: <your-server-ip>
  14. 14.# TTL: 3600
  15. 15.`
  16. 16.Verify the wildcard record is propagating: Check DNS resolution.
  17. 17.```bash
  18. 18.dig site1.example.com A +short
  19. 19.# Should return: <your-server-ip>
  20. 20.dig any-subdomain.example.com A +short
  21. 21.# Should also return: <your-server-ip>
  22. 22.`
  23. 23.Verify Apache/Nginx is configured for wildcard subdomains: Check server configuration.
  24. 24.```apache
  25. 25.# Apache: ServerAlias should include wildcard
  26. 26.ServerAlias *.example.com

# Nginx: server_name should include wildcard server_name example.com *.example.com; ```

  1. 1.Test the subdomain site in WordPress: Confirm the site is accessible.
  2. 2.`
  3. 3.# Visit https://site1.example.com
  4. 4.# Should load the WordPress multisite subdomain
  5. 5.# Check WordPress Network Admin > Sites > site1 > Visit
  6. 6.`

Prevention

  • Configure wildcard DNS A records when setting up WordPress multisite with subdomains
  • Document DNS requirements for WordPress multisite in the hosting setup guide
  • Monitor subdomain DNS resolution after any DNS configuration changes
  • Use DNS management tools that support bulk record verification
  • Include wildcard DNS verification in the WordPress multisite setup checklist
  • Test new subdomain site creation immediately to catch DNS issues early