Gre Configuration; Creating Virtual Tunnel Interface - 3Com 3C13636 Configuration Manual

3Com Router 3000 Ethernet Family
Configuration Guide
present. When transmitting such multicast data as routing protocol, voice and image in
an IPSec tunnel, you can set up a GRE tunnel, encapsulate the multicast data with
GRE, and then encrypt the encapsulated data using IPSec. Thus, data secrecy in
transmission can be achieved.
In addition, GRE also supports users to select and record identification key of tunnel
interface, and supports the end-to-end check of encapsulated message.
Due to the influence of such factors as encapsulation and decapsulation between GRE
sender and receiver and data increase caused by encapsulation, the use of GRE may
somewhat decrease the data forwarding efficiency of routers.

3.2 GRE Configuration

Among all the configuration tasks, virtual tunnel interface must be created first before
other function features can be configured on it. Deleting a virtual tunnel interface
deletes all configurations on it.
GRE configuration tasks include:
Create virtual tunnel interface (required)
Set encapsulation mode (optional)
Specify source end of tunnel (required)
Specify destination end of tunnel (required)
Set network address of tunnel interface (required)
Configure end-to-end verification on both ends of tunnel (optional)
Set identification key of tunnel interface (optional)
Configure routing via tunnel (optional)

3.2.1 Creating Virtual Tunnel Interface

Virtual tunnel interface should be created so that other parameters of GRE can be
configured on it. These configurations are required to be performed on both ends of the
tunnel.
Perform the following configuration in system view.
Table 3-1 Create virtual tunnel interface
Create a virtual tunnel interface.
Delete a virtual tunnel interface.
By default, no virtual tunnel interface is created.
The device adopts distributed structure, on which interfaces are represented in a
three-dimension way, i.e, slot/card/port. The parameter slot represents slot number of
the specified universal interface module; card represents the number of the installed
Operation
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3-4
Chapter 3 Configuration of GRE
Command
interface tunnel number
undo interface tunnel number