Basic OSPF network topology

Note that other subnets can be added to the internal interfaces without changing the configuration.

 

Assumptions

• The FortiGate units used in this example have interfaces named port1, port2, and port3.
• All FortiGate units in this example have factory default configuration with FortiOS 4.0 MR2 firmware installed, and are in NAT/Route operation mode.
• Basic firewalls are in place to allow unfiltered traffic between all connected interfaces in both directions.
• This OSPF network is not connected to any other OSPF networks.
• Both Internet connections are always available.
• The modem connection is very slow and expensive.
• Other devices may be on the network, but do not affect this basic configuration.
• Router3 is responsible for redistributing all routes into and out of the OSPF AS.

 

Configuring the FortiGate units

Each FortiGate unit needs the interfaces, and basic system information such as hostname configured. This section includes:

• Configuring Router1
• Configuring Router2
• Configuring Router3

 

Configuring Router1

Router1 has two interfaces connected to the network—internal (port1) and external (port2). Its host name must be changed to Router1.

To configure Router1 interfaces – web-based manager

1. Go to System > Dashboard > Status.

2. Beside the host name, select Change.

3. Enter a hostname of Router1, and select OK.

4. Go to System > Network > Interfaces, edit port1, set the following information, and select OK.

Alias                                           internal

IP/Network Mask                       10.11.101.1/255.255.255.0

Administrative Access             HTTPS SSH PING

Description                                Head office and Router2

Administrative Status               Up

5. Edit port2, set the following information, and select OK.

Alias                                           External

IP/Network Mask                       10.11.102.1/255.255.255.0

Administrative Access             HTTPS SSH PING

Description                                Router3

Administrative Status               Up

Configuring Router2

 

Router2 configuration is the same as Router1, except Router2 also has the DSL interface to configure.

The DSL interface is configured with a username of “user1” and a password of “ospf_example”. The default gateway will be retrieved from the ISP, and the defaults will be used for the rest of the PPPoE settings.

To configure Router2 interfaces – web-based manager

1. Go to System > Dashboard > Status.

2. Beside the host name, select Change.

3. Enter a hostname of Router2, and select OK.

4. Go to System > Network > Interfaces, edit port1, set the following information, and select OK.

Alias                                           internal

IP/Network Mask                       10.11.101.2/255.255.255.0

Administrative Access             HTTPS SSH PING

Description                                Head office and Router1

Administrative Status               Up

5. Edit port2, set the following information, and select OK.

Alias                                           External

IP/Network Mask                       10.11.103.2/255.255.255.0

Administrative Access             HTTPS SSH PING

Description                                Router3

Administrative Status               Up

6. Edit DSL (port3), set the following information, and select OK.

Alias                                           DSL

Addressing Mode                     PPPoE

Username                                   user1

Password                                   ospf_example

Unnumbered IP                         10.12.101.2/255.255.255.0

Retrieve default gateway from server

Enable

Administrative Access             HTTPS SSH PING

Description                                DSL

Administrative Status               Up

Configuring Router3

Router3 is similar to Router1 and Router2 configurations. The main difference is the External (port3) interface connected to the ISP BGP network which has no administration access enabled for security reasons.