User's Manual

43-5
Chapter 43 GRE Tunnel Configuration
43.1 Introduction to GRE Tunnel
GRE (General Routing-protocol Encapsulation) was referred to IETF by Cisco and Net-smiths companies in
1994, in RFC1701 and RFC1702. At present, the network devices of the most manufacturers support the
GRE tunnel protocol. GRE set how to encapsulate a kind of network protocol in other kind of network protocol.
The GRE tunnel is defined by the source IP address and the destination IP address of two ends, it allows that
users can use IP packets to encapsulate IP, IPX, AppleTalk packets, and supports all routing protocols (such
as RIP2, OSPF, etc). By GRE, users can use the public IP network to connect IPX network, AppleTalk network,
and use the reserved address to connect through the internet work, or hide the IP address of the corporation
network to the public network. GRE only provides the encapsulation of the data packets, and has no
encryption function to avoid the network interception and attack. Therefore, it is used with IPsec usually in the
actual environment, and IPsec provides the data encryption to supply very good security for users.
The most use of GRE protocol: the internal protocol encapsulation and the private address encapsulation of
the enterprise. In our nation, the enterprise network almost adopts TCP/IP protocol, so there are fewer
requirements to the internal protocol encapsulation. The enterprise use GRE almost for encapsulating the
private address .In our switches, the GRE is used mainly for the transition of the network protocol (include
IPv6 OVER IPv4 and IPv4 OVER IPv6).
RFC1701, 1702, 2784 are referred for the implement.
43.2 GRE Tunnel Basic Configuration
GRE Tunnel Configuration Task List:
1. Configure tunnel mode
1) Configure tunnel mode as GREv4 tunnel
2) Configure tunnel mode as GREv6 tunnel
2. Configure the source address and the destination address of GRE tunnel
1) Configure the source address as the IPv6 or IPv4 address for GRE tunnel
2) Configure the destination address as the IPv6 or IPv4 address for GRE tunnel
3. Configure the interface address of GRE tunnel
1) Configure the IPv4 address of GRE tunnel interface
2) Configure the IPv6 address of GRE tunnel interface
4. Configure the egress interface of the static route as GRE tunnel
1) Configure the egress interface of the IPv4 static route to GRE tunnel
2) Configure the egress interface of the IPv6 static route to GRE tunnel