Eicon Networks SHIVA 1100, Administrator'S Manual, Page: 96 / 136

GRE
96 System Administrator’s Guide
GRE
The GRE configuration of the Shiva VPN Gateway allows you to build GRE tunnels to
other devices that support the Generic Routing Encapsulating protocol. You can build
GRE tunnels to other Shiva VPN Gateways that support GRE, or to other devices such
as Cisco equipment.
GRE tunnels are useful for redistributing IPv6 or broadcast and multicast traffic across
a VPN connection. It is also useful for carrying unsupported protocols such as IPX or
Appletalk between remote IP networks.
Warning
GRE tunnels are not secure unless they are run over another secure protocol. Using
a GRE tunnel that runs over the Internet, it is possible for an attacker to put packets
onto your network. If you want a tunneling mechanism to securely connect to
networks, then you should use IPSec, or tunnel GRE over either IPSec or PPTP
tunnels.
An example setup that describes using GRE to bridge a network over an IPSec tunnel
is described in GRE over IPSec.
Setting up a GRE tunnel
For this example we will connect two office networks using a GRE tunnel between two
Shiva VPN Gateways. One is located in Brisbane, the other in Slough. The two
networks have the following configuration:
Shiva VPN Gateway in Brisbane
• Internet address: 203.23.45.6
• LAN address: 192.168.1.1
• LAN: 192.168.1.0 / 255.255.255.0
Shiva VPN Gateway in Slough
• Internet address: 195.45.67.8
• LAN address: 10.1.0.1
• LAN: 10.1.0.0 / 255.255.0.0
1 On the Brisbane end, click GRE Tunnels from the VPN menu. Enter the
following details:
• GRE Tunnel Name: to_slough
• Remote External Address: 195.45.67.8
• Local External Address: 203.23.45.6
• Local Internal Address: 192.168.1.1
2. Click Add .
3. Click Add/Remove under Remote Networks and enter:
Remote subnet/netmask: 10.1.0.0 /255.255.0.0