An IPsec (ESP or AH) mode that is applied to an IP tunnel, where an outer IP packet header (of an intermediate destination) is added on top of the original, inner IP header. In this case, the ESP or AH transform treats the inner IP header as if it were part of the packet payload. When the packet reaches the intermediate destination, the tunnel terminates and both the outer IP packet header and the IPsec ESP or AH transform are taken out.
The process of tunneling, as opposed to "transport mode."
ESP mode that encrypts an entire IP packet including the IP header.
Encapsulation in which the entire original IP datagram is encrypted, and it becomes the payload in a new IP packet. This mode allows a network device, such as a router, to act as an IPSec proxy. The router performs encryption on behalf of the hosts. The source's router encrypts packets and forwards them along the IPSec tunnel. The destination's router decrypts the original IP datagram and forwards it on to the destination system. Tunnel mode is typically used in a gateway-to-gateway connection.
An IPSec mode of operation where the entire IP packet, including IP header is authenticated and/or encrypted and a new IP header is addedâ€”protecting the entire original packet. Both VPN clients and VPN gateways can use this mode. Compare to Transport Mode
IPSec mode of operation in which the entire IP packet, including the header, is encrypted and authenticated and a new VPN header is added, protecting the entire original packet. This mode can be used by both VPN clients and VPN gateways, and protects communications that come from or go to non-IPSec systems. See also transport mode.