You can use IPsec to protect a VPN. For background, see Transport and Tunnel Modes in IPsec. The examples and procedures in this section use IPv4 addresses, but the examples and procedures apply to IPv6 VPNs as well. For a short discussion, see Protecting Network Traffic With IPsec.
For examples of IPsec policies for tunnel mode, see Examples of Protecting a VPN With IPsec by Using Tunnel Mode.