• Use Session Key: 1
• Additional Encapsulation Checksum: Enabled
3. Define a route in the main routing table which routes all traffic to remote_net_B on the
GRE_to_B GRE interface. This is not necessary if the option Add route for remote network
is enabled in the Advanced tab, since this will add the route automatically.
4. Create the following rules in the IP rule set that allow traffic to pass through the tunnel:
Name Action Src Int Src Net Dest Int Dest Net Service
To_B Allow lan lannet GRE_to_B remote_net_B all_services
From_B Allow GRE_to_B remote_net_B lan lannet all_services
Part 2. Setup for NetDefend Firewall B
Assuming that the network 192.168.11.0/24 is lannet on the lan interface, the steps for setting up
NetDefendOS on B are as follows:
1. In the address book set up the following IP objects:
• remote_net_A: 192.168.10.0/24
• remote_gw: 172.16.0.1
• ip_GRE: 192.168.0.2
2. Create a GRE Tunnel object called GRE_to_A with the following parameters:
• IP Address: ip_GRE
• Remote Network: remote_net_A
• Remote Endpoint: remote_gw
• Use Session Key: 1
• Additional Encapsulation Checksum: Enabled
3. Define a route in the main routing table which routes all traffic to remote_net_A on the
GRE_to_A GRE interface. This is not necessary if the option Add route for remote network
is enabled in the Advanced tab, since this will add the route automatically.
4. Create the following rules in the IP rule set that allow traffic to pass through the tunnel:
Name Action Src Int Src Net Dest Int Dest Net Service
To_A Allow lan lannet GRE_to_A remote_net_A all_services
From_A Allow GRE_to_A remote_net_A lan lannet all_services
Checking GRE Tunnel Status
IPsec tunnels have a status of being either up or not up. With GRE tunnels in NetDefendOS this
does not really apply. The GRE tunnel is up if it exists in the configuration.
However, we can check on the what is going on with a GRE tunnel. For example, if the tunnel is
Chapter 3: Fundamentals
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