28 lines
1.8 KiB
Markdown
28 lines
1.8 KiB
Markdown
```mermaid
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graph TB;
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Upstream["dns.google (8.8.8.8; 8.8.4.4)"]
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Clients["Clients [192.168.1.0/24]"]
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Router["VyOS Router [192.168.1.1]"]
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PiHoles["PiHole [192.168.1.22,192.168.1.21]"]
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BlackHole["Black Hole"]
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Clients --"First connect"--> Router
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Router --"Sends DHCP with DNS=192.168.1.22,192.168.1.21"--> Clients
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Clients --"Subsequent requests"--> PiHoles
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Router ----> PiHoles
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PiHoles --"Blacklisted domains"--> BlackHole
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PiHoles --"Valid requests"--> Upstream
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```
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Clients connecting to the local network for the first time will receive as part of the DHCP negotiation ([code 6](https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol#Information)) the domain name servers' addresses. These addresses will correspond to the IP addresses of the PiHole servers (currently RasPis at `192.168.1.22` and `192.168.1.21`).
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From that point, clients will send simultaneous DNS requests to both Piholes and use the first response received. This means the PiHoles will be able to track requests per-client. However, this splits tracking data between the two servers, so it may be difficult to visualize a complete picture.
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A client can be manually configured to request DNS resolution from the router, which will forward requests to the PiHoles.
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DNS requests to the PiHole will be checked against the [configured adlists](https://pihole.jafner.net/groups-adlists.php). If matched, the request will be blocked. If a user is attempting to access a website that is blocked, the request should quickly resolve to a Domain Not Found error. It will look like this:
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If the request does not match any adlists, it will be passed upstream to Google `8.8.8.8` (or backup `8.8.4.4`).
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Presently, the PiHole does not cache any requests.
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