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I have an unbound DNS Resolver in my office lab. I m using this service to block ads and unwanted domains.

Is there any possibilities to redirect DNS quires to a specific URL/DNS that shows the site/DNS is blocked like "opendns" service? .

or

Do you guys know if there any alternative method to build own servers like opendns, quad9 ..etc using opensource tools ?

James Arems
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    You can't go from a DNS query to an URL. But you can configure unbound (and many other resolvers) to intercept queries for specific domains/hosts like bad.example.com and instead of the actual IP-address return the ip-address of your own webserver. On that web server you can then display a friendly error message. The problem will be that your server won't have valid TLS certificates for sites that you block and users will get to see a browser error instead of a webpage. See https://paulgorman.org/technical/dns_filtering_with_unbound.txt for an example – HBruijn Feb 28 '19 at 07:43

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Is there any possibilities to redirect DNS quires to a specific URL/DNS that shows the site/DNS is blocked like "opendns" service?

Of course: Just set up a web server that serves that page to any request, and make your DNS point at that server for any domain you want to block. If you want to start blocking specific URLs in addition to entire domains, however, you'll spend the rest of your life writing rules or whitelisting false positives...

Do you guys know if there any alternative method to build own servers like opendns, quad9 ..etc using opensource tools ?

The world is pretty much built on BIND which is kind of open...

Mikael H
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