The suggested answer is D. Wire Mode.
Wire Mode allows VPN connections to maintain a secure session without Stateful Inspection.
The main reason is that Wire Mode treats VPN traffic as trusted by defining internal interfaces and communities as "trusted", effectively bypassing stateful inspection. This is particularly useful in scenarios where stateful inspection might interfere with VPN protocols or introduce performance overhead. It relies on a pre-established trust between the VPN endpoints.
While Stateless Mode (Option B) might seem relevant, it doesn't directly address the VPN connection maintenance in the same way as Wire Mode. Stateless Mode generally refers to a firewall operating without keeping track of the state of network connections, but it doesn't inherently create a secure VPN session. Therefore, it is not the most appropriate answer in the context of the question.
VPN Routing Mode (Option A) is a general term for how VPN traffic is routed and doesn't specifically address bypassing stateful inspection.
Stateful Mode (Option C) is the opposite of what the question asks for, as it explicitly involves Stateful Inspection.