proxy_bind

proxy_bind指令强制将与代理主机的连接绑定到指定的IP地址。通俗来讲就是，在配置了多个基于名称或者基于IP的主机的情况下，如果我们希望代理连接由指定的主机处理，就可以使用该指令进行配置，其语法结构为：

proxy_bind address;

其中，address为指定主机的IP地址。

If your proxy server has several network interfaces, sometimes you might need to choose a particular source IP address for connecting to a proxied server or an upstream. This may be useful if a proxied server behind NGINX is configured to accept connections from particular IP networks or IP address ranges.