Could not flush the DNS Resolver Cache is an error message that you may receive when you run the ipconfig /flushdns command on Windows machines.
The DNS Client service is used by the Windows operating system to resolve and store DNS (domain name system) information in order to speed up the process on consecutive uses.
The DNS cache is enabled by default, and will cache DNS requests for most programs that connect to the Internet.
There are a few possible pitfalls that users experience when using the DNS cache in the Windows operating system.
One of them is that the information in the DNS cache is outdated. This may lead to loading issues when you are connecting to sites or servers. The ipconfig /flushdns command can be used to flush the dns cache in order to resolve the domain names anew.
Flushing means clearing the cache, so that no information is stored in it after the operation. This forces Windows to use the configured DNS server to pull the DNS information.
Users who try to flush the dns cache may receive the error message "Windows IP Configuration Could not flush the DNS Resolver Cache: Function failed during execution".
The error message is identical on all recent versions of the Windows operating system including Windows 7 and Windows 10.
The most likely reason for that is that the DNS Client service is deactivated.
The solution to fix this error message is to enable the DNS Client service in the Services configuration menu. I'm not sure if it makes that much sense to flush the cache if the DNS Client is disabled, as it means that Windows is not resolving and storing DNS at all.
Tip: you can run the command ipconfig /displaydns after enabling the DNS Client to list all cached DNS entries that Windows stored in the cache at the time of running the command.
Basically, what it means is that Windows won't cache DNS requests if the DNS Client service is disabled. Flushing the DNS cache therefore does not have a positive effect on the system.
You need to set the service to manual or automatic under "startup type" before the start option becomes available. Select Start to start up the service.
When you return to the command prompt afterwards, flushing the DNS cache using ipconfig /flushdns should work as expected.
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