Why are some URLs blocked even after adding them to the whitelist?

Zyxel_Stanley

Scenario:
I have setup some of DNS Content Filter categories as block rule first, and then I add multiple URL into "Allow List", but the website still blocked by DNS Content Filter rule.

Answer:
This issue might be occurring because the DNS content filter works by using DNS cache. When you add URLs to the "Allow List", they might still get blocked due to old DNS entries in the cache.

How to resolve:
Please try to flush DNS cache in PC and firewall to see if the issue is resolved.

PC:
C:/> ipconfig /flushdns

Firewall:
Router(config)# ip dns server cache-flush