UpdatedDecember 11, 2024

How to check from your firewall if ISP is blocking access to a website

Description

Learn how to check if your firewall is blocking a website. Follow this guide to troubleshoot access issues due to firewall settings.

In this article, you will see how you can troubleshoot website connectivity from your firewall. Whether it is a website that you are trying to access for the first time and it is not working, or it is a website that was working fine the past days and suddenly it stopped loading, the following procedure will help you find if the issue is related to the Sonicwall.

Resolution for SonicOS 7.X

This release includes significant user interface changes and many new features that are different from the SonicOS 6.5 and earlier firmware. The below resolution is for customers using SonicOS 7.X firmware.

The first thing to do is to find out the IP address of the website you are trying to access.
To do this, open a command prompt on your PC and type "nslookup website name" (for example nslookup google.com)

In this case here, the IP address of the website would be 142.250.189.206. After finding out the IP address of the website, the next step is to troubleshoot the connection between the firewall and that website.

Login to the firewall management interface and Navigate to Monitor|Tools & Monitor | Packet Monitor
On General | Monitor Filter tab, destination IP address should be the one of the website that is not accessible.
After you save the settings, start the packet capture from the first tab Captured Packets.
Refresh the website so you get some traffic captured.
If you are seeing dropped packets, then that means the firewall is indeed dropping packets in the connection with that website. Based on the drop code, we can check why the connection is terminated/dropped.
If your packets are forwarded/generated, please make sure the destination is correct. If not, look for any bad route policies, arp entries etc.

If you still require assistance, please contact Technical Support

There are two ways to contact technical support:

Online: Visit MySonicWALL Website. Once logged in select Resources & Support | Support | Create Case.
By phone: please use our toll-free number at 1-888-793-2830. Please have your SonicWall serial number available to create a new support case.

Resolution for SonicOS 6.5

This release includes significant user interface changes and many new features that are different from the SonicOS 6.2 and earlier firmware. The below resolution is for customers using SonicOS 6.5 firmware.

Login to the firewall management interface and Navigate to Investigate| Tools | Packet Monitor
Click Configure at the bottom and On Monitor Filter tab, destination IP address should be the one of the website that is not accessible.
After you save the settings, start the packet capture from the first tab Captured Packets.
Refresh the website so you get some traffic captured.
If you are seeing dropped packets, then that means the firewall is indeed dropping packets in the connection with that website. Based on the drop code, we can check why the connection is terminated/dropped.
If your packets are forwarded/generated, please make sure the destination is correct. If not, look for any bad route policies, arp entries etc.