I'm attempting to set up an Enterprise Portal collaboration with ArcGIS online, and noted that in the list of pre-requisites listed here: Create a collaboration—Portal for ArcGIS (10.6) | ArcGIS Enterprise that each participant is required to trust the SSL certificate used by the other participants. If my Enterprise Portal instance is internal, and uses a domain CA signed certificate, how can I go about registering this with ArcGIS Online? If this is not possible, would this mean that my internal Enterprise portal must use a commercial CA, such as digicert?
When setting up a collaboration between Enterprise and Online, you don't need to worry about the certificate trust. Online uses certificates signed by DigiCert and your Enterprise already trusts those. Since your Enterprise is on an internal network, all network communication will be initiated from your Enterprise so Online will not need to trust your internal domain CA certificates.