To configure an isolated bridge group for Integrated Routing and Bridging (IRB) mode on a Cisco Secure Firewall device, the action to take is to leave the BVI (Bridge Virtual Interface) interface name empty. This ensures that the bridge group operates in an isolated manner, where Layer 3 routing is not applied to the bridged interfaces, effectively isolating the traffic within the bridge group.

Steps:

Access the firewall's configuration interface.

Configure the bridge group interfaces.

Ensure that the BVI interface name is left empty to isolate the bridge group.

This configuration prevents Layer 3 routing for the isolated bridge group, ensuring that traffic remains contained within the bridge group.