DNS is the service that resolve domain (eg. example.com) to IP address (xx.xx.xx.xx).
Because MultiSite create a subdomain for each new website, you have to make sure that all subdomains resolve to the same IP. Sometimes it is the default configuration if not, you have to add wildcard subdomain setting in your domain name provider control panel.
How to check if your DNS setings are OK. Open command line and enter
- ping example.com
- ping www.example.com
- ping xxx.example.com
All these commands should all be pinging the same IP address. If you see "unknown host" error, that means, DNS is not configured properly.
If you are using cPanel, here is short tutorial how to fix that.
If you have access to DNS setup, add following record:
*.example.com. 3600 IN A [[YourIP]]
Please keep in mind, that DNS records are cached by your computer and internet provider.
Please refer to your registrar or hosting company if you need help.