20
01-28004-0019-20040830
Fortinet Inc.
NAT/Route mode
Getting started
NAT/Route mode
In NAT/Route mode, the FortiGate unit is visible to the network. Like a router, all its
interfaces are on different subnets. The following interfaces are available in
NAT/Route mode:
• External is the interface to the external network (usually the Internet).
• Internal is the interface to the internal network.
• DMZ is the interface to the DMZ network.
You can add firewall policies to control whether communications through the
FortiGate unit operate in NAT or Route mode. Firewall policies control the flow of
traffic based on the source address, destination address, and service of each packet.
In NAT mode, the FortiGate unit performs network address translation before it sends
the packet to the destination network. In Route mode, there is no address translation.
You typically use NAT/Route mode when the FortiGate unit is operating as a gateway
between private and public networks. In this configuration, you would create NAT
mode firewall policies to control traffic flowing between the internal, private network
and the external, public network (usually the Internet).
If you have multiple internal networks, such as a DMZ network in addition to the
internal, private network, you could create route mode firewall policies for traffic
flowing between them.
Figure 5: Example NAT/Route mode network configuration
NAT/Route mode with multiple external network connections
In NAT/Route mode, you can 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).
• DMZ 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.
FortiGate-100 Unit
in NAT/Route mode
Route mode policies
controlling traffic between
internal networks.
Internal network
DMZ network
Internal
192.168.1.1
DMZ
10.10.10.2
192.168.1.3
10.10.10.23
External
204.23.1.5
NAT mode policies controlling
traffic between internal and
external networks.
Internet
INTERNAL
EXTERNAL
DMZ
POWER
STATUS