There are actually a number of places where DNS caching could be taking place, including your computer, your modem/router (if it is acting as a DNS relay) or your ISPs DNS servers.
If you are running Windows and wish to clear its DNS cache, use the command ipconfig /flushdns
The method of clearing the DNS cache on your modem/router will vary depending on the unit. It might be easier just to restart the device.
As for your ISPs DNS cache; Unfortunately, you have no control over this.
Also, as mentioned above, the issue you are seeing may not be caused by caching at all. It could be that the DNS for your domain has not fully propagated yet.
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