Reference" https://www.cisco.com/c/en/us/td/docs/security/firepower/620/configuration/guide/fpmc-config-guide-v62/working_with_intrusion_events.html

Secure Firewall Management Center must trust the certificate presented by the Cisco ISE pxGrid server.
Therefore, the certificate authority certificate that signed the pxGrid node's server certificate must be exported from ISE and imported into Management Center as a trusted CA object. If primary and secondary pxGrid nodes are deployed, Cisco requires their certificates to be signed by the same trusted certificate authority.
Depending on the integration design, the engineer might also need the monitoring-node CA certificate and a pxGrid client certificate with its private key for Management Center. However, the question specifically asks which certificate establishes trust with the pxGrid server node. SAML and domain-controller certificates are unrelated, and a certificate cannot simultaneously be self-signed and signed by a third-party CA. Cisco ISE and Secure Firewall certificate integration

To change the mode of a Cisco Secure Firewall Threat Defense (FTD) device in the Cisco Secure Firewall Management Center (FMC) inventory, the engineer must follow these steps:
* Register the Secure FTD with Secure FMC.
* Change the firewall mode.
* Deregister the Secure FTD device from Secure FMC.
To perform these actions, accessing the Secure FTD CLI from the console port is necessary. This allows the engineer to execute the required commands to change the firewall mode and manage the registration status of the FTD device.
Steps:
* Connect to the Secure FTD device via the console port.
* Access the CLI and execute the command to change the firewall mode (configure firewall-mode).
* Deregister the device from FMC if needed.
* Register or re-register the device with FMC as required.
References: Cisco Secure Firewall Threat Defense Configuration Guide, Chapter on Device Management and CLI Access.

Reference: https://www.cisco.com/c/en/us/td/docs/security/firepower/fxos/clustering/ftd-cluster-solution.
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