3Com 10014299 Configuring GRE

638 CHAPTER 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 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
Creating a Virtual Tunnel
Interface Perform the following tasks in the system view.
Tabl e 687 Create Virtual Tunnel Interface
By default, no virtual tunnel interface is created.
Setting the Source
Address of a Tunnel
Interface
After a tunnel interface is created, the source address of tunnel channel must be
configured. The source address is the address of the physical interface where the
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.
Tabl e 688 Set the Source Address of Tunnel Interface
By default, no source address of the tunnel interface is configured.
Operation Command
Create virtual tunnel interface and enter
tunnel view. interface tunnel tunnel-number
Cancel virtual tunnel interface. undo interface tunnel
Operation Command
Set the source address of tunnel interface. source ip-address
Delete the configured source address of
tunnel the interface. undo source