HTTP proxy external server definitions support the following configuration properties:

server-host-name
The resolvable name or IP address of the HTTP proxy server to use. This is required.
server-port
The port on which the HTTP proxy server is listening for connections. This is required.
basic-authentication-username
The username to use if the proxy server requires authentication. This should be omitted if the proxy server does not require authentication.
basic-authentication-passphrase-provider
The passphrase provider to use to obtain the password to use if the proxy server requires authentication. This should be omitted if the proxy server does not require authentication.

For example, you can use a configuration change like the following to create an HTTP proxy external server that does not require authentication:

dsconfig create-external-server \
     --server-name "Example HTTP Proxy Server" \
     --type http-proxy \
     --set server-host-name:proxy.example.com \
     --set server-port:3128