If your Zynstra server is going to sit behind a firewall, you will need to configure your firewall to let the necessary traffic through.
You need to open up the following ports to allow the required traffic to pass through your firewall:
From the Internet to the Zynstra server WAN IP address:
From the Zynstra server WAN IP address to the Internet:
All ports open
From the Internet to the Zynstra server iLO IP address:
And ONLY if you have dual node cluster, you will also have to open up these ports to the second (iLO IP address):