Link Aggregation – FortiBalancer

Chapter 3 Link Aggregation

3.1 Overview

This section describes link aggregation functionality of the network. Link Aggregation is also called trunking, which can greatly improve network performance and stability.

3.2 Understanding Link Aggregation

Link Aggregation or trunking is a method of combining physical network links into a single logical link for increased bandwidth. With Link Aggregation, we are able to increase the capacity and availability of the communication channel between devices. Two or more Gigabit Ethernet connections are combined in order to increase the bandwidth capability and create resilient and redundant links.

The FortiBalancer appliance supports at most 6 bond interfaces, and at most 12 system interfaces can be added to a bond interface. The bond interface will check the status of the system interfaces. If a system interface becomes down, the traffic processed by this interface will be directed to other working system interfaces in the bond interface.

To add a system interface into a bond interface, the administrator can further set the interface as the primary or backup interface in the bond. Multiple primary or backup interfaces can be set in a bond. When all the primary interfaces in the bond fail, the backup interfaces will take the place of primary interfaces to work.

Note: To bind a system interface with a bond interface, the system interface should be configured with no IP address information. If there is IP configuration on the system interface, the administrator needs to remove the IP configuration first. If otherwise, the system will refuse to add the system interface into the bond.

In addition, the FortiBalancer appliance also supports configuring MNET or VLAN on bond interface. The bond interface configuration must be performed before configuring MNET or VLAN on it.

3.3 Link Aggregation Configuration

3.3.1 Configuration Guidelines

Before you start to configure link aggregation, please take a moment to familiarize yourself with the network architecture for link aggregation configuration.


Figure 3-1 Link Aggregation Configuration

Table 3-1 General Settings of Link Aggregation

Operation Command
Bond system interfaces bond interface <bond_name> <interface_name> [1|0]
Operation Command
Assign a name for the bond interface bond name <bond_id> <bond_name>
Assign IP address to the bond interface ip address {system_ifname|mnet_ifname|vlan_ifname|bond_ifname} <ip_address> {netmask|prefix}
Assign default route ip route default <gateway_ip>

3.3.2 Configuration Example via CLI

  • Step 1 Bind system interfaces with bond interface

In our example, we bind the “port1” interface and the “port4” interface with the bond interface bond1, and further set the “port1” interface as the primary, and “port4” as the backup in the bond interface.

FortiBalancer(config)#bond interface bond1 port1 1

FortiBalancer(config)#bond interface bond1 port4 0

  • Step 2 Assign a name for the bond interface

We can set the bond name for the configured bond interface by using the “bond name” command.

FortiBalancer(config)#bond name bond1 link1

  • Step 3 Assign an IP address and netmask to the bond interface

FortiBalancer(config)#ip address link1

  • Step 4 Set the gateway IP address

FortiBalancer(config)#ip route default

To verify that FortiBalancer appliance is indeed actively deployed within this network infrastructure, you may ping the gateway IP by using the “ping” command.

If these configurations are entered correctly, you will receive the following return messages.


PING 56 data bytes

64 bytes from icmp_seq=0 ttl=128 time=0.671 ms

64 bytes from icmp_seq=1 ttl=128 time=0.580 ms

64 bytes from icmp_seq=2 ttl=128 time=0.529 ms

64 bytes from icmp_seq=3 ttl=128 time=0.486 ms

64 bytes from icmp_seq=4 ttl=128 time=0.638 ms



— ping statistics —

5 packets transmitted, 5 packets received, 0% packet loss round-trip min/avg/max/stddev = 0.486/0.581/0.671/0.068 ms

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