The `proxy_protocol` in Nginx is used to forward the original client IP address along with the request under certain circumstances, such as when the client is behind a load balancer or a reverse proxy. If you're setting up a chain of Nginx servers forwarding requests to each other (also known as "proxy chaining"), whether you need to enable the `proxy_protocol` on each subsequent Nginx instance depends on whether you need the original client IP address to be passed along to the next server in the chain. Here's the scenario: 1. If you want every server in the chain to know the original client IP address, then you would need to enable `proxy_protocol` on each Nginx server in the chain. This is because the `proxy_protocol` line containing the client IP address is consumed by the Nginx server that reads it, and if it's not added back in when forwarding the request to the next server, the next server won't receive it. 2. If only the final server in the chain needs to know the original client IP address, then it's sufficient to enable `proxy_protocol` on the first Nginx server and the final server. The intermediate servers can forward the requests without `proxy_protocol`. Remember to configure both the sending and the receiving ends when you use `proxy_protocol`. On the sending side, you should use `proxy_pass` with the `proxy_protocol` option. On the receiving side, you should use `listen` with the `proxy_protocol` option. Also, keep in mind that `proxy_protocol` may not be compatible with all backends. The backend server needs to understand and parse the `proxy_protocol` to extract the client's real IP. --gpt-4-web

To carry the original client IP address from the first to the third server in a chain of three Nginx servers, you would need to use the PROXY protocol. Here is an example of how you can configure the Nginx instances. 1. **First Nginx Server (Source IP Collector)** You don't need to enable PROXY protocol on the first server. It just needs to pass along the information to the second server. ```nginx stream { server { listen 12345; proxy_pass server2:12345; proxy_protocol on; } } ``` 2. **Second Nginx Server (Middle Forwarder)** The second server needs to accept the PROXY protocol from the first server and then send the PROXY protocol line to the third server. ```nginx stream { server { listen 12345 proxy_protocol; proxy_pass server3:12345; proxy_protocol on; } } ``` 3. **Third Nginx Server (Destination IP Resolver)** The third server needs to accept the PROXY protocol from the second server. It then uses the original client IP for its processing. ```nginx stream { server { listen 12345 proxy_protocol; # the actual processing goes here # the original client IP is available in the $proxy_protocol_addr variable } } ``` Replace `12345` with your actual port number, and `server2` and `server3` with the actual addresses of your second and third servers. Please note that you should adjust your firewall rules to allow traffic on the ports used by the servers. Also, these configurations should be placed in the `nginx.conf` file, or in separate configuration files included from the main `nginx.conf` file. --gpt-4-web

No, it can't. If you don't use the `proxy_protocol` on the second server, the original client IP address won't be forwarded from the first server to the third server. In your chain of Nginx servers, the `proxy_protocol` option is used to add a line at the start of the request with the original client IP address. When the first server sends this line to the second server, the second server needs to accept the `proxy_protocol` to understand this line. If it doesn't, it would just forward the request as is to the third server, without the original client IP address. So, the second server needs to use the `proxy_protocol` in its `listen` directive to accept the line with the original client IP from the first server, and it also needs to use the `proxy_protocol` in its `proxy_pass` directive to add this line back into the request when forwarding it to the third server. Here is the correct configuration for the second server: ```nginx stream { server { listen 12345 proxy_protocol; proxy_pass server3:12345; proxy_protocol on; } } ``` This tells the second server to expect the `proxy_protocol` line in the requests it receives from the first server, and to also add the `proxy_protocol` line into the requests it forwards to the third server. --gpt-4-web

Apologies for the confusion. You're correct. In the context of a `stream` block, if the first Nginx server sends a `proxy_protocol` header, and the second server is merely forwarding traffic without modifying it, the `proxy_protocol` header should be included in what gets forwarded. The `proxy_protocol` directive in the `listen` statement on the second server is used to configure that server to understand the `proxy_protocol` header. However, if the second server isn't actually interpreting the traffic and is just passing it along, you may not need to include `proxy_protocol` in its `listen` directive. Here is the adjusted configuration: 1. **First Nginx Server (Source IP Collector)** ```nginx stream { server { listen 12345; proxy_pass server2:12345; proxy_protocol on; } } ``` 2. **Second Nginx Server (Middle Forwarder)** ```nginx stream { server { listen 12345; proxy_pass server3:12345; } } ``` 3. **Third Nginx Server (Destination IP Resolver)** ```nginx stream { server { listen 12345 proxy_protocol; # the actual processing goes here # the original client IP is available in the $proxy_protocol_addr variable } } ``` This configuration assumes that the second server is only forwarding the traffic and not processing it. If the second server needs to process the traffic in some way (for example, if it needs to make decisions based on the original client IP), then it would need to include `proxy_protocol` in its `listen` directive. Thanks for bringing up this point, and I apologize for any confusion in my previous responses. --gpt-4-web