Forward proxy and reverse proxy are two common proxy server architectures, which play different roles and application scenarios in network communications.

1. Forward Proxy:
A forward proxy is a proxy server that sits between a client and a target server. When a client needs to access resources on the Internet, it first sends the request to the forward proxy server, which then sends the request on behalf of the client and receives the response. The client usually needs to configure the address and port of the proxy server.

Application scenarios:

Break through network access restrictions: In some network environments, access to specific websites or resources may be restricted. By using a forward proxy, clients can indirectly access restricted resources.
Anonymous browsing: Forward proxy can hide the client's real IP address, provide a certain degree of anonymity, and protect privacy.
Caching and performance optimization: Proxy servers can cache requested resources, reduce network transmission, and increase access speed.
2. Reverse Proxy:
A reverse proxy is a proxy server that sits between the target server and the client. When clients send requests, they are received by the reverse proxy server, which forwards the request to one or more backend servers on behalf of the client. The backend servers process the request and send responses back to the reverse proxy server, which then returns the response to the client.

Application scenarios:

Load balancing: The reverse proxy can distribute requests to multiple backend servers, balancing server loads and improving system scalability and performance.
Security and protection: Reverse proxy can hide the real IP address of the backend server, providing a certain degree of security and protection. It can filter malicious requests, prevent DDoS attacks, etc.
Caching and acceleration: Reverse proxy can cache static resources, reduce the load on the backend server, and improve response speed.
SSL encryption and decryption: The reverse proxy can handle SSL/TLS connections and provide secure HTTPS services to the outside world.
3. Application of nginx
Nginx can act as both a forward proxy and a reverse proxy through appropriate configuration file settings. The specific configuration reference is as follows:

Forward proxy configuration

server {
listen 80;
server_name proxy.example.com;

 location / { resolver 8.8.8.8; proxy_pass http://$http_host$request_uri; proxy_set_header Host $http_host; proxy_set_header X-Real-IP $remote_addr; }

}

Reverse proxy configuration

server {
listen 80;
server_name example.com;

 location / { proxy_pass http://backend_servers; proxy_set_header Host $http_host; proxy_set_header X-Real-IP $remote_addr; }

}

upstream backend_servers {
server backend1.example.com;
server backend2.example.com;
# Add more backend servers…
}
For a forward proxy, server_name specifies the domain name or IP address of the proxy server. In the location / block, proxy_pass specifies the target address of the proxy request, and proxy_set_header is used to set the request header information.

For reverse proxy, server_name specifies the domain name or IP address of the reverse proxy server. In the location / block, proxy_pass specifies the address of the backend server, and proxy_set_header is used to set the request header information. The upstream block defines a list of backend servers.