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GRE Configuration

This chapter includes these sections:

•

GRE Overview

•

Configuring a GRE over IPv4 Tunnel

•

Configuring a GRE over IPv6 Tunnel

•

Displaying and Maintaining GRE

•

GRE over IPv4 Tunnel Configuration Example

•

GRE over IPv6 Tunnel Configuration Example

•

Troubleshooting GRE

GRE Overview

Introduction to GRE

Generic Routing Encapsulation (GRE) is a protocol designed for encapsulating and carrying the packets

of one network layer protocol (for example, IP) over another network layer protocol (for example, IP).

GRE is a tunneling technology and serves as a Layer 3 tunneling protocol.

A GER tunnel is a virtual point-to-point (P2P) connection for transferring encapsulated packets. Packets

are encapsulated at one end of the tunnel and de-encapsulated at the other end.

Figure 1 depicts the

encapsulation and de-encapsulation processes.

Figure 1 X protocol networks interconnected through the GRE tunnel

The following takes the network shown in

Figure 1 as an example to describe how an X protocol packet

traverses the IP network through a GRE tunnel.

Encapsulation process

1. After receiving an X protocol packet through the interface connected to Group 1, Device A submits

it to the X protocol for processing.

2. The X protocol checks the destination address field in the packet header to determine how to route

the packet.

3. If the packet must be tunneled to reach its destination, Device A sends it to the tunnel interface.

4. Upon receipt of the packet, the tunnel interface encapsulates it in a GRE packet. Then, the system

encapsulates the packet in an IP packet and forwards the IP packet based on its destination

address and the routing table.

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H3c-technologies H3C SecPath F1000-E Manual de usuario Pagina 2