2.1 Introduction to GRE
The transmission of packets in a GRE tunnel involves two processes: encapsulation and
decapsulation. After receiving a packet of a certain network layer protocol such as IPX that needs
to be encapsulated and routed, the system adds a GRE header to the packet, and then encapsulates
the packet into a packet of another protocol such as IP.
GRE encapsulates the packets of certain network layer protocols such as IP and IPX. After
encapsulation, these packets can be transmitted over the network by another network layer
protocol, such as IP.
GRE can serve as a Layer 3 tunneling protocol for VPNs. A tunnel is a virtual point-to-point
connection and can be regarded as a virtual interface that supports only point-to-point
connections. This interface provides a path to transmit encapsulated datagrams. GRE
encapsulates and decapsulates datagrams at both ends of the tunnel.
2.2 GRE Features Supported by the S7700
GRE features supported the S7700 include the following: multi-protocol local network
transmission through the single-protocol backbone network, enlargement of the operation scope
of the network running a hop-limited protocol (like IPX), connection of some discontinuous
subnets to establish a VPN, and working in conjunction with IPSec to compensate the flaw of
IPSec in multicast data protection.
Multi-Protocol Local Network Transmission Through Single-Protocol Backbone
Network
In
, Group 1 and Group 2 are the local networks running the Novell IPX protocol.
Team 1 and Team 2 are the local networks running the IP protocol.
Figure 2-1
Networking diagram of multi-protocol local network transmission through the
single-protocol backbone network
GRE Tunnel
Internet
SwitchA
SwitchB
Novell IPX
Group 1
IP
Team 1
IP
Team 2
Novell IPX
Group 2
Quidway S7700 Smart Routing Switch
Configuration Guide - VPN
2 GRE Configuration
Issue 01 (2011-07-15)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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