An engineer plans to reconfigure an existing Cisco FTD from transparent mode to routed mode. Which additional action must be taken to maintain communication between the two network segments?

Assigning unique VLAN IDs is good practice but doesn't address the fundamental requirement of IP subnets for routing; VLANs are layer 2 segmentation.

In transparent mode, the FTD acts as a bump-in-the-wire and interfaces are in the same broadcast domain and often the same IP subnet. When converting to routed mode, the FTD acts as a router, and each interface must belong to a different IP subnet to allow for proper routing between segments. This is a fundamental requirement for a routed device.

While NAT might be used for other purposes, it's not a direct requirement to "maintain communication" between segments when transitioning to routed mode; proper routing between distinct subnets is the primary concern.

Deploying inbound ACLs is a security measure to control traffic, but the primary enabler for communication between different routed segments is correct IP addressing and routing, not just ACLs. ACLs would be applied after routing is established.