After creating or changing a domain, a subdomain or a DNS record, the name may still answer "unknown domain" or return the old address for a while. This article explains why, and how to check what our servers actually publish.
In short: A change is only online after Synchronize in the DNS manager, then caches keep the old answer until the TTL expires (four hours by default). Query ns1.swisscenter.com to see what we publish.
Prerequisites
- Access to a terminal (or command prompt) on your computer (Linux/Unix, macOS, or Windows).
- The domain is managed by SwissCenter to use the proposed example command.
What you need to know before you start
- A change is only published after synchronization. As long as the DNS manager shows the banner "DNS configuration is not synchronized with DNS servers", your changes are not online yet: click Synchronize.
- Resolvers keep answers in cache. Each record has a time to live (TTL), four hours by default in the DNS manager. A resolver that has already queried the name keeps the old answer until this delay expires; some Internet Service Providers (ISPs) keep it longer.
- An "unknown" answer is cached too. If a subdomain was requested before it was created, your router or ISP may keep the "unknown domain" information for the period defined by its cache, which generates this error.
The delay therefore depends on the caches between you and our servers: we cannot guarantee how long it takes.
How do I check what our servers publish?
Query the relevant server directly, for example, if the domain is managed by SwissCenter:
On Linux/Unix/macOS:
Run the following command from a terminal:
host mondomaine.tld ns1.swisscenter.com
The command dig @ns1.swisscenter.com mondomaine.tld gives the same result, with more details.
On Windows:
Run the following command from a terminal:
nslookup mondomaine.tld ns1.swisscenter.com
Repeat this operation for the relevant subdomain (for example www). You will then see what information will be propagated on the Internet once the information's time to live and your provider's or router's cache have expired.
If something goes wrong
- Our servers still return the old value: the change has not been published. Check in the DNS manager that no synchronization is pending, then look at the DNS change history to see what was actually published and when.
- Our servers return the right value, but your computer does not: it is a cache. Restarting your router as well as your computer can sometimes force the update of their DNS cache; otherwise, wait until it expires.
- For an outside view without a terminal, analyze the name with diag.swisscenter.com (the tool is in French): in the Entrées Web & Mail (web and mail records) card, the Serveur Web (A) section shows the address that a resolver on the Internet receives, or « Pas d'entrée A trouvée pour » (no A record found for) followed by the name if it has none. The tool also goes through a caching resolver: if it shows the new value while your computer shows the old one, the cache is on your side. It removes
www. from the name you enter: for www, keep using the command above. See Diagnose your domain and email with the SwissCenter diagnostic tool.
Going further