Gre Tunnels - D-Link NetDefend DFL-210 User Manual

3.3.5. GRE Tunnels

• Service Name: Service name provided by the service provider
• Username: Username provided by the service provider
• Password: Password provided by the service provider
• Confirm Password: Retype the password
• Under Authentication specify which authentication protocol to use
(the default settings will be used if not specified)
• Disable the option Enable dial-on-demand
• Under Advanced, if Add route for remote network is enabled then a new route will be added for the
interface
3. Click OK
3.3.5. GRE Tunnels
Overview
The Generic Router Encapsulation (GRE) protocol is a simple, encapsulating protocol that can be
used whenever there is a need to tunnel traffic across networks and/or through network devices.
GRE does not provide any security features but this means that its use has extremely low overhead.
Using GRE
GRE is typically used to provide a method of connecting two networks together across a third
network such as the Internet. The two networks being connected together communicate with a
common protocol which is tunneled using GRE through the intervening network. Examples of GRE
usage are:
• Traversing network equipment that blocks a particular protocol.
• Tunneling IPv6 traffic across an IPv4 network.
• Where a UDP data stream is to be multicast and it is necessary to transit through a network
device which does not support multicasting. GRE allows tunneling though the network device.
GRE Security and Performance
A GRE tunnel does not use any encryption for the communication and is therefore not, in itself,
secure. Any security must come from the protocol being tunneled. The advantage of GRE's lack of
encryption is the high performance which is achievable because of the low traffic processing
overhead. The lack of encryption can be acceptable in some circumstances if the tunneling is done
across an internal network that is not public.
Setting Up GRE
Like other tunnels in NetDefendOS such as an IPsec tunnel, a GRE Tunnel is treated as a logical
interface by NetDefendOS, with the same filtering, traffic shaping and configuration capabilities as
a standard interface. The GRE options are:
Note
To provide a point-to-point connection over Ethernet, each PPP session must learn the
Ethernet address of the remote peer, as well as establish a unique session identifier.
PPPoE includes a discovery protocol that provides this.
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Chapter 3. Fundamentals