Prisma Access egress and public IP addresses can change as a result of autoscaling or infrastructure upgrades, so any allow-list dependent on those addresses (SaaS tenant restrictions, partner firewalls, third-party services) needs a reliable way to stay current. Palo Alto Networks addresses this with two complementary mechanisms. First, an Egress IP Notification URL — the webhook referenced in option A — can be configured under Infrastructure Settings so that Prisma Access sends an HTTP POST a few seconds before a new IP address becomes active, giving downstream automation advance warning to update firewall or SaaS allow-lists before the change takes effect. Second, retrieving the actual address list requires authenticating to the Egress/Public IP retrieval API using an API key that is generated and copied from the service infrastructure settings, as described in option B; this key is passed in the request header when calling the retrieval endpoint. There is no separate " enable the Egress IP API endpoint " toggle, since the retrieval API is available by default once a key is generated — making option C incorrect. Authentication to this API is strictly key-based, not certificate-based, so downloading a client certificate (option D) is not a supported or required step. Together, the webhook and API key form the complete automation loop: notify, then retrieve and apply.