3Com 10014299 manual Configuring GRE, By default, no virtual tunnel interface is created

638CHAPTER 44: CONFIGURING GRE

The two sub-networks group1 and group2 that are running the Novell IPX protocol are in different cities. With the tunnel available, the trans-WAN VPN can be established.

In addition, GRE also allows users to select and record an identification key word for the tunnel interface, a check of the encapsulated message, and the use of synchronous sequence numbers to ensure channel safety and correctness of transmission data.

Encapsulation and de-encapsulation on the GRE receiving side and transmitting side increases overhead cost and the increase in data volume caused by encapsulation also increases bandwidth cost. for these reasons, GRE decreases the forwarding rate of router data to some extent.

Configuring GRE

Creating a Virtual Tunnel Interface

GRE configuration includes:

■Creating a Virtual Tunnel Interface

■Setting the Source Address of a Tunnel Interface

■Setting the Destination Address of a Tunnel Interface

■Setting the Network Address of the Tunnel Interface

■Setting the Identification Key Word of the Tunnel Interface

■Setting the Tunnel Interface to Check with Checksum

■Settng the Tunnel Interface to Synchronize the Datagram Sequence Number

Perform the following tasks in the system view.

Table 687 Create Virtual Tunnel Interface

Operation	Command
Create virtual tunnel interface and enter	interface tunnel tunnel-number
tunnel view.
Cancel virtual tunnel interface.	undo interface tunnel

By default, no virtual tunnel interface is created.

Setting the Source After a tunnel interface is created, the source address of tunnel channel must be Address of a Tunnel configured. The source address is the address of the physical interface where the Interface GRE packets are transmitted. The source address and destination address of the

tunnel interface uniquely identifies a channel. These configurations must be implemented at both tunnel ends, and furthermore, the source address of one end must be the destination address of another end.

Perform the following settings in the tunnel interface view.

Table 688 Set the Source Address of Tunnel Interface

Operation	Command
Set the source address of tunnel interface.	source ip-address
Delete the configured source address of	undo source
tunnel the interface.

By default, no source address of the tunnel interface is configured.