Disclaimer: This information is provided as-is for the benefit of the Community. Please contact Sophos Professional Services if you require assistance with your specific environment.
Table of Contents
Overview
This article provides some of the basic steps a Sophos Firewall administrator can take while troubleshooting issues related to a Website being blocked or partially blocked.
Error Codes
It’s important to identify why a Website was blocked (completely or partially). Suppose you receive an HTTP error code that helps you understand what happened. I've listed some of the most common Client and Server error codes. The 4xx error codes mean that client requests contain bad syntax or can't be fulfilled due to an invalid or improper request. The 5xx error code means the server failed to fulfill a valid request.
4×× Client Error
- 400 Bad Request
- 401 Unauthorized
- 403 Forbidden
- 404 Not Found
- 405 Method Not Allowed
- 406 Not Acceptable
- 407 Proxy Authentication Required
- 408 Request Timeout
- 409 Conflict
- 414 Request-URI Too Long
- 415 Unsupported Media Type
- 416 Requested Range Not Satisfiable
- 417 Expectation Failed
- 429 Too Many Requests
- 431 Request Header Fields Too Large
- 444 Connection Closed Without Response
5×× Server Error
- 500 Internal Server Error
- 501 Not Implemented
- 502 Bad Gateway
- 503 Service Unavailable
- 504 Gateway Timeout
- 505 HTTP Version Not Supported
- 511 Network Authentication Required
- 599 Network Connect Timeout Error
Troubleshooting
The first thing you should identify is Web Filtering is applied to the firewall rule, which allows/processes the traffic. You should be able to identify the Firewall rule by following this KBA Sophos Firewall: Monitor traffic using packet capture. Once the firewall rule is identified, please check whether a WebFilter policy is applied.
A) If a Web Filter policy isn’t applied, you should try to open the website from SSH of the Sophos Firewall. You can use a curl or wget command.
i.e. wget --no-check-certificate https://www.sophos.com or curl -v https://www.sophos.com
- If the connection was successful, there's no issue from the ISP while connecting the website.
- You should check the drop-packet-capture using this KBA Sophos Firewall: Monitor traffic using packet captureand find why it’s being dropped.
In the Advanced Shell of Sophos Firewall, you could type drppkt host <hostname or ip-address-of-website> and port <web-site-port>
for example,
# drppkt host sophos.com and port 443 - Check for any value in drop-packet-capture that might indicate an issue with the traffic.
- If none of the above helps, please post the error screenshot and details on the Sophos Firewall community forum, or if you have a valid support license, create a case with Sophos Support.
- You should check the drop-packet-capture using this KBA Sophos Firewall: Monitor traffic using packet captureand find why it’s being dropped.
- If the connection wasn’t successful, it might be from an ISP or upstream network devices, as connections from SSH are unfiltered and attempted from the active WAN port of the Sophos Firewall. If it's feasible, try changing the active internet gateway of the Sophos Firewall and see if the issue persists.
B) If a Web Filter policy is applied, please check if the Web Policy is configured to allow or block the request. Please refer to this KBA Sophos Firewall : Policy Tester.
- If it’s shown as allowed in the Policy test tool, follow these steps:
- Check the drop-packet capture for the traffic and discover why it’s being dropped.
- Check for any value in drop-packet-capture that might indicate an issue with the traffic.
- Do a TCPDUMP and see for any connection error from the web server.
- If none of the above helps, please post the error screenshot and details on the Sophos Firewall community forum, or if you have a valid support license, create a case with Sophos Support.
- Check the drop-packet capture for the traffic and discover why it’s being dropped.
- If it shows as Not Allowed or Blocked, please allow the Website in the Web Filter policy or create an exception for the specific user/IP to allow access to the Website.
Updated Links to latest, grammar
[edited by: Raphael Alganes at 3:08 PM (GMT -8) on 12 Nov 2024]