In the documentation related to Zero downtime Upgrade Process, it is stated that:"Should you use a PROXY and a firewall in the systems used for the upgrade, ports will have to be configured accordingly."Which ports are they ??
There are 2 separate port ranges when using ZDU : one for the original AE and one for the new version. Ports are used by server processes of the newer version may have to be opened on Proxy / firewall if needed.
You can find a list of this port inside the ucsrv.ini of the automation engine folder, for example here what we have here in our lab: