IPSec is a suite of protocols used to secure communications between peers. IPSec provides strong cryptographic security services to protect sensitive data and ensures network privacy and integrity. IPSec can be configured to provide security for a wide range of network topologies, including site-to-site and remote access connections.

In IPSec, you can configure various settings, such as encryption and authentication algorithms and security associations timeouts. One such configuration is the IPSec mode—tunnel mode or transport mode.

Tunnel mode is commonly used in site-to-site VPNs where the communication between the complete networks or subnets needs to be protected. Transport mode is commonly used in end-to-end encryption between hosts. You can choose a tunnel or transport mode based on your network structure and data security requirements.

While configuring an IPSec tunnel, you can select the IPSec mode as tunnel or transport mode to establish a secure connection. That is, you can select whether to encrypt or authenticate packets in tunnel mode or transport mode. PAN-OS^® supports tunnel mode by default, authenticating or encrypting the data (IP packet) as it traverses the tunnel. Beginning with PAN-OS 11.0.0, you can use transport mode.