private Properties createLocatorConfig(int systemId, int locatorPort, int remoteLocatorPort) {
    Properties config = new Properties();
    config.setProperty(MCAST_PORT, "0");
    config.setProperty(DISTRIBUTED_SYSTEM_ID, String.valueOf(systemId));
    config.setProperty(LOCATORS, "localhost[" + locatorPort + ']');
    config.setProperty(REMOTE_LOCATORS, "localhost[" + remoteLocatorPort + ']');
    config.setProperty(START_LOCATOR,
        "localhost[" + locatorPort + "],server=true,peer=true,hostname-for-clients=localhost");
    config.setProperty(SECURITY_PEER_AUTH_INIT, TestPeerAuthInitialize.class.getName() + ".create");
    config.setProperty(SECURITY_PEER_AUTHENTICATOR,
        TestPeerAuthenticator.class.getName() + ".create");
    config.setProperty(USER_NAME, "user");
    config.setProperty(PASSWORD, "user");
    return config;
  }
Use of SECURITY_CLIENT_AUTHENTICATOR should result in the servers performing authentication
during HandShake of Gateway Sender/Receiver connecting.
geode-wan/src/distributedTest/java/org/apache/geode/internal/cache/wan/GatewayLegacyAuthenticationRegressionTest.java