IPsec aggregate for redundancy and traffic load-balancing

This is a sample configuration of a multiple site-to-site IPsec VPN that uses an IPsec aggregate interface to set up redundancy and traffic load-balancing. The VPN tunnel interfaces must have net-device disabled in order to be members of the IPsec aggregate.

Each FortiGate has two WAN interfaces connected to different ISPs. OSPF runs over the IPsec aggregate in this configuration.

The supported load balancing algorithms are: L3, L4, round-robin (default), weighted round-robin, and redundant. The first four options allow traffic to be load-balanced, while the last option (redundant) uses the first tunnel that is up for all traffic.

Dynamic routing can run on the aggregate interface, and it can be a member interface in SD-WAN (not shown in this configuration).

Configuring the HQ1 FortiGate in the GUI

There are five steps to configure the FortiGate:

1. Create the IPsec tunnels.
2. Create the IPsec aggregate.
3. Configure the firewall policies.
4. Configure the aggregate VPN interface IPs.
5. Configure OSPF.

To create the IPsec tunnels:

1. Go to VPN > IPsec Wizard and select the Custom template.

2. For Name, enter pri_HQ2 and click Next.

3. Enter the following:

   Phase 1
   IP Address	172.16.202.1
   Interface	port1
   Device creation	Disabled
   Aggregate member	Enabled
   Authentication Method	Pre-shared Key
   Pre-shared Key	Enter the secure key
   IKE Mode	Aggressive
   Peer Options Accept Types	Any peer ID
   Phase 2
   Auto-negotiate	Enable

4. Configure the other settings as needed.

5. Click OK.

6. Create another tunnel named sec_HQ2 with the following settings:

   Phase 1
   IP Address	172.17.202.1
   Interface	port2
   Device creation	Disabled
   Aggregate member	Enabled
   Authentication Method	Pre-shared Key
   Pre-shared Key	Enter the secure key
   IKE Mode	Aggressive
   Peer Options Accept Types	Any peer ID
   Phase 2
   Auto-negotiate	Enable

To create the IPsec aggregate:

1. Go to VPN > IPsec Tunnels and click Create New > IPsec Aggregate.
2. For Name, enter agg_HQ2.
3. Select a load balancing algorithm.
4. From the Tunnel dropdown, select the tunnels that you created previously (pri_HQ2 and sec_HQ2). If required, enter weights for each tunnel.
5. Click OK.

To configure the firewall policies:

1. Go to Policy & Objects > Firewall Policy.

2. Create an inbound traffic policy with the following settings:

   Name	inbound
   Incoming Interface	agg_HQ2
   Outgoing Interface	dmz
   Source	172.16.101.0
   Destination	10.1.100.0
   Schedule	always
   Action	ACCEPT
   Service	ALL

3. Click OK.

4. Create an outbound traffic policy with the following settings:

   Name	outbound
   Incoming Interface	dmz
   Outgoing Interface	agg_HQ2
   Source	10.1.100.0
   Destination	172.16.101.0
   Schedule	always
   Action	ACCEPT
   Service	ALL

To configure the aggregate VPN interface IPs:

1. Go to Network > Interfaces and edit agg_HQ2.
2. For IP, enter 10.10.10.1.
3. For Remote IP/Netmask, enter 10.10.10.2 255.255.255.255.
4. Click OK.

To configure OSPF:

1. Go to Network > OSPF.
2. For Router ID, enter 1.1.1.1.
3. In the Areas table, click Create New.
   1. For Area ID, enter 0.0.0.0.
   2. Click OK.
4. In the Networks table, click Create New.
   1. Set the Area to 0.0.0.0.
   2. For IP/Netmask, enter 10.1.100.0/24.
   3. Click OK.
   4. Click Create New.
   5. For IP/Netmask, enter 10.10.10.0/24.
   6. Click OK.
5. Click Apply.

Configuring the HQ2 FortiGate in the GUI

There are five steps to configure the FortiGate:

1. Create the IPsec tunnels.
2. Create the IPsec aggregate.
3. Configure the firewall policies.
4. Configure the aggregate VPN interface IPs.
5. Configure OSPF.

To create the IPsec tunnels:

1. Go to VPN > IPsec Wizard and select the Custom template.

2. For Name, enter pri_HQ1 and click Next.

3. Enter the following:

   Phase 1
   IP Address	172.16.200.1
   Interface	port25
   Device creation	Disabled
   Aggregate member	Enabled
   Authentication Method	Pre-shared Key
   Pre-shared Key	Enter the secure key
   IKE Mode	Aggressive
   Peer Options Accept Types	Any peer ID
   Phase 2
   Auto-negotiate	Enable

4. Configure the other settings as needed.

5. Click OK.

6. Create another tunnel named sec_HQ1 with the following settings:

   Phase 1
   IP Address	172.17.200.1
   Interface	port26
   Device creation	Disabled
   Aggregate member	Enabled
   Authentication Method	Pre-shared Key
   Pre-shared Key	Enter the secure key
   IKE Mode	Aggressive
   Peer Options Accept Types	Any peer ID
   Phase 2
   Auto-negotiate	Enable

To create the IPsec aggregate:

1. Go to VPN > IPsec Tunnels and click Create New > IPsec Aggregate.
2. For Name, enter agg_HQ1.
3. Select a load balancing algorithm.
4. From the Tunnel dropdown, select the tunnels that you created previously (pri_HQ1 and sec_HQ1). If required, enter weights for each tunnel.
5. Click OK.

To configure the firewall policies:

1. Go to Policy & Objects > Firewall Policy.

2. Create an inbound traffic policy with the following settings:

   Name	inbound
   Incoming Interface	agg_HQ1
   Outgoing Interface	port9
   Source	10.1.100.0
   Destination	172.16.101.0
   Schedule	always
   Action	ACCEPT
   Service	ALL

3. Click OK.

4. Create an outbound traffic policy with the following settings:

   Name	outbound
   Incoming Interface	port9
   Outgoing Interface	agg_HQ1
   Source	172.16.101.0
   Destination	10.1.100.0