The first host you install ECE on initially requires the ports for all roles to be open, which includes the ports for the coordinator, allocator, director, and proxy roles. After you have brought up your initial ECE installation, only the ports for the roles that the initial host continues to hold need to remain open. Before installing a runner, make sure that the 20000, 21000, 22000 ports are open for the installation script checks.

During a typical installation, internet access is required unless you are doing an offline installation.