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01-28008-0017-20050128
Fortinet Inc.
Planning the FortiGate configuration
Getting started
Figure 6: Example NAT/Route mode network configuration
NAT/Route mode with multiple external network connections
In NAT/Route mode, you can use the modem interface to configure the FortiGate unit
with multiple redundant connections to the external network (usually the Internet). For
example, you could create the following configuration:
• External is the default interface to the external network (usually the Internet).
• Modem is the redundant interface to the external network.
• Internal is the interface to the internal network.
You must configure routing to support redundant Internet connections. Routing can be
used to automatically redirect connections from an interface if its connection to the
external network fails.
Otherwise, security policy configuration is similar to a NAT/Route mode configuration
with a single Internet connection. You would create NAT mode firewall policies to
control traffic flowing between the internal, private network and the external, public
network (usually the Internet).
Figure 7: Example NAT/Route multiple internet connection configuration
Transparent mode
In Transparent mode, the FortiGate unit is invisible to the network. Similar to a
network bridge, all FortiGate interfaces must be on the same subnet. You only have to
configure a management IP address so that you can make configuration changes.
The management IP address is also used for antivirus and attack definition updates.
You typically use the FortiGate unit in Transparent mode on a private network behind
an existing firewall or behind a router. The FortiGate unit performs firewall functions,
IPSec VPN, virus scanning, IPS, web content filtering, and Spam filtering.
FortiGate-50A Unit
in NAT/Route mode
Internal network
Internal
192.168.1.99
192.168.1.3
External
204.23.1.5
NAT mode policies controlling
traffic between internal and
external networks.
POWER
Internet
INTERNAL
EXTERNAL
LINK 100
LINK 100
PWR
STATUS
A
FortiGate-50A Unit
in NAT/Route mode
External
204.23.1.5
Modem
NAT mode policies controlling
traffic between internal and
external networks.
Internet
Internal
192.168.1.1
Internal network
192.168.1.3
INTERNAL
EXTERNAL
LINK 100
LINK 100
PWR
STATUS
A