Why can't I access the websites? It appears to be unexpectedly blocked by the firewall

Zyxel_Jeff

Scenario :

Why can't I access websites? Such as Youtube.

If checking the returned certificate notice the DNS name is dnsft.cloud.zyxel.com. It appears to be unexpectedly blocked by the Zyxel firewall.

Answer :

There is a way to diagnose this problem.

STEP1. Please use the CLI "nslookup www.youtube.com 8.8.8.8" to check if Youtube URL can be resolved normally by Google DNS server in your environment or not.

STEP2. Please the CLI "nslookup www.youtube.com" to check what is the IP address of Youtube URL on your PC's DNS server.

Based on the above nslookup example, it's evident that the resolved results are different. When using 'nslookup www.youtube.com,' the result is resolved to the DNS server's address 192.170.X.X, not the correct address for YouTube. Therefore, this issue is related to the DNS server's cache problem. To resolve it, please clean the DNS server's cache or change the preferred DNS server on your PC to 8.8.8.8.

Below is Win10 PC's preferred DNS Server setting.

Below is Win11 PC's preferred DNS Server setting.