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You simply have to link the Ngrok container to the application under the `app` or `http` or `https` aliases, and all of the configuration will be done for you by default.
Additionally, you can specify one of several environment variable (via `-e`) to configure your Ngrok tunnel:
*`NGROK_AUTH` - Authentication key for your Ngrok account. This is needed for custom subdomains, custom domains, and HTTP authentication.
*`NGROK_SUBDOMAIN` - Name of the custom subdomain to use for your tunnel. You must also provide the authentication token.
*`NGROK_HOSTNAME` - Paying Ngrok customers can specify a custom domain. Only one subdomain or domain can be specified, with the domain taking priority.
*`NGROK_USERNAME` - Username to use for HTTP authentication on the tunnel. You must also specify an authentication token.
*`NGROK_PASSWORD` - Password to use for HTTP authentication on the tunnel. You must also specify an authentication token.
*`NGROK_PROTOCOL` - Can either be `HTTP` or `TCP`, and it defaults to `HTTP` if not specified. If set to `TCP`, Ngrok will allocate a port instead of a subdomain and proxy TCP requests directly to your application.
*`NGROK_PORT` - Port to expose (defaults to `80` for `HTTP` protocol).