pfSense » pfSense Docs

Reference: https://docs.netgate.com/pfsense/en/latest/vpn/ipsec/compatibility.html#terminology-differences

Include ProxyIDs. Palo Alto firewalls strictly use tunnel interfaces (VTI) and so ProxyIDs must be used. Generally used to define phase2 traffic.

Supporting documentation: https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA10g000000ClW8CAK

Ran into this issue the other day where the client needed to set ProxyIDs in their configuration and was unsure what that was even for.