Redundant interfaces
On the FortiMail unit, you can combine two or more physical interfaces to provide link redundancy. This feature allows you to connect to two or more switches to ensure connectivity in the event one physical interface or the equipment on that interface fails.
In a redundant interface, traffic is only going over one interface at any time. This differs from an aggregated interface where traffic is going over all interfaces for increased bandwidth. This difference means redundant interfaces can have more robust configurations with fewer possible points of failure. This is important in a fully-meshed HA configuration.
A physical interface is available to be in a redundant interface if:
- it is a physical interface, not a VLAN interface
- it is not already part of a redundant interface
- it has no defined IP address and is not configured for DHCP
- it does not have any VLAN subinterfaces
- it is not monitored by HA
When a physical interface is included in a redundant interface, it is not listed on the System > Network > Interface page. You cannot configure the interface anymore.
For information about adding redundant interfaces, see “Configuring the network interfaces” on page 247.
Loopback interfaces
A loopback interface is a logical interface that is always up (no physical link dependency) and the attached subnet is always present in the routing table.
The FortiMail’s loopback IP address does not depend on one specific external port, and is therefore possible to access it through several physical or VLAN interfaces. In the current release, you can only add one loopback interface on the FortiMail unit.
The loopback interface is useful when you use a layer 2 load balancer in front of several FortiMail units. In this case, you can set the FortiMail loopback interface’s IP address the same as the load balancer’s IP address and thus the FortiMail unit can pick up the traffic forwarded to it from the load balancer.
For information about adding a loopback interface, see “Configuring the network interfaces” on page 247.