Which network access method could be used to investigate a storage appliance that has lost all network access?

The scenario presented involves a storage appliance that has lost all network access, indicating that remote network-based methods of access would be ineffective in this case. The correct choice relates to a direct form of access that does not depend on the network infrastructure.

Using a console port provides a direct interface to the device. This method typically involves connecting a computer or laptop directly to the storage appliance's console port using a serial cable. The console port allows administrators to interact with the device's command-line interface directly, bypassing any network-related issues. This method is essential for initial configurations, troubleshooting, and recovery of devices that can no longer communicate over the network. It does not rely on the state of the network, making it reliable for accessing the device in a situation where it has lost network connectivity.

The other options, such as HTTP, RDP, and SSH, are network-based remote access methods that require the device to have network connectivity. This makes them unsuitable for investigating a device that has already lost all means of network access. Therefore, utilizing the console port is the most effective approach in this scenario.