Fortinet 127, 500A, FORTIGATE, Network Router NAT/Route mode with multiple external network connections

Getting started NAT/Route mode with multiple external network connections

FortiGate-500A Installation Guide 01-28005-0101-20041015 21

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:

• LAN is the interface to the internal network.

• Port 1 is the default interface to the external network (usually the Internet).

• Port 2 is the redundant interface to the external 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).

FortiGate-500A Unit

in NAT/Route mode

Route mode policies

controlling traffic between

internal networks.

Internal network

DMZ network

Port 1

192.168.1.99

Port 4

10.10.10.1

192.168.1.3

10.10.10.2

Port 2

204.23.1.5

NAT mode policies controlling

traffic between internal and

external networks.

Internet

Esc Enter

CONSOLE

USB LAN

1234

L1 L2 L3 L4

10/100 10/100/1000