H3C Technologies H3C S12500 Series Switches - Manual (Page 213)

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Configuring tunneling
Overview
Tunneling is an encapsulation technology: one network protocol encapsulates packets of another
network protocol and transfers them over a virtual point-to-point connection. The virtual connection is
called a tunnel. Packets are encapsulated and de-encapsulated at both ends of a tunnel. Tunneling refers
to the whole process from data encapsulation to data transfer to data de-encapsulation.
Tunneling provides the following features:
• Transition techniques, such as IPv6 over IPv4 tunneling, to interconnect IPv4 and IPv6 networks.
• Virtual Private Networks (VPNs) for guaranteeing communication security, such as Generic Routing
Encapsulation (GRE).
• Traffic engineering, such as Multiprotocol Label Switching traffic engineering (MPLS TE), to prevent
network congestion.
The preceding tunneling technologies require that you create virtual Layer 3 interfaces (tunnel interfaces)
at both ends of a tunnel, so that switches at both ends can send, identify, and process packets transferred
through the tunnel.
The term "tunnel" used throughout this document refers to an IPv4/IPv6 tunnel.
For more information about GRE and MPLS TE, see "Configuring GRE" and MPLS Configuration Guide.
IPv6 over IPv4 tunnel
Implementation
IPv6 over IPv4 tunneling adds an IPv4 header to IPv6 data packets so that IPv6 packets can pass an IPv4
network through a tunnel to realize interworking between isolated IPv6 networks, as shown in
Figure 85 .
The IPv6 over IPv4 tunnel can be established between two hosts, a host and a device, or two devices. The
tunnel destination node can forward IPv6 packets if it is not the destination of the IPv6 packets.
NOTE:
The devices at both ends of an IPv6 over IPv4 tunnel must support the IPv4/IPv6 dual stack.