The communication from the Selenium Hub to the RCs requires that the high ports are generally open between the master and the slave.
In our environment, such a setup is not viable. A possibility would be to go over a proxy as described here: http://selenium-grid.seleniumhq.org/faq.html#can_i_configure_the_remote_control_to_use_a_custom_httphttps_proxy
The environment properties on the general hudson configuration page do not apply here. I did not find a possibility to set system properties with -D during startup of the hub jar:
Starting Selenium Grid
[selenium-grid] $ /usr/java/jdk1.6.0_30/jre/bin/java -cp /opt/hudson/data/war/WEB-INF/lib/remoting-1.395.jar hudson.remoting.Launcher -cp /opt/hudson/data/selenium-grid/li
b/log4j-1.2.14.jar:/opt/hudson/data/selenium-grid/lib/selenium-grid-hub-standalone-1.0.4.jar -connectTo localhost:48365
Is that possible somewhere? If not, could it be added?