Internet Filter Content Filter

Is there any risk in Using IP Lookup when uploading a Master List to a custom category?

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Remember, with IP Lookup enabled, filtering will take place by IP address as well. So if the custom category is set to a Block List, then IP addresses that correspond to URLs in the uploaded file will be blocked along with the URLs. Conversely, if the custom category is set to an Allow List, then IP addresses that correspond to URLs in the uploaded file will be allowed along with the URLs.

Depending on how your DNS handles certain web requests, you may run into the risk of different URLs resolving to the same web host IP address, which is common among smaller websites. This can pose a problem if you have the following scenario:

  • Custom category CustomAllow sits in the Allow List of a profile.
  • Custom category CustomBlock sits in the Block List.
  • CustomAllow contains www.goodurl.com
  • CustomBlock contains www.badurl.com
  • www.goodurl.com and www.badurl.com are both hosted by the same site and both resolve to IP address 209.254.254.254
  • IP Lookup was used when uploading the Master List for both of these custom categories
In this situation, the IP address 209.254.254.254 will reside in both CustomAllow and CustomBlock. Remember, the Allow List takes precedence over Block in the filtering hierarchy. So if a user with this profile goes to www.badurl.com, in some situations depending on your DNS, R3000 will see this request as 209.254.254.254. Thus, since this IP address exists in a category contained within the Allow List, the request will not be blocked.