Layer 3 Interfaces
An ECMP set is formed when the routing table contains multiple next-hop address for the same destination with
equal cost.
Routes of equal cost have the same preference and metric value. If there is an ECMP set for an active route, the
switch uses a hash algorithm to choose one of the next-hop addresses.
As input to the hash, the switch uses one or more of the following fields in the packet to be routed: Source IP,
Destination IP, or Input Port.
Configuring ECMP
The switch will automatically use ECMP to choose between equal-cost routes.
As input to the hash, you can configure the switch to use one or more of the following fields in the packet to be
routed: Source IP, Destination IP, or Input Port.
This configuration value is system-wide. Source IP is the default value.
Notes and Restrictions
Maximum of 8 alternative paths (i.e. ecmp path).
When you configure a static route with a gateway, the gateway must be in the same IPsubnet as the device.
Also, the destination subnet cannot be equal to any of device IP subnets in the system.
When you configure a static route without a gateway, the destination subnet be in the same IPsubnet as the
device.
Using the CLI:
config system setting
set v4-ecmp-mode [ source-ip-based ] [ dst-ip-based ] [ port-based ]
end
Example ECMPConfiguration
The following is an example CLI configuration for ECMP forwarding.
In this configuration, we configure Port2 and Port6 as routed ports. We create interfaces I-RED and I-GREEN as
RVI interface. The remaining ports in the switch are normal Layer 2 ports.
1. Configure Native VLANs for Port2, Port6 and Port9. Also configure “internal” interface to allow native VLANs for
Port2, Port6 and Port9.:
config switch interface
edit port2
set native-vlan 10
edit port6
set native-vlan 20
edit port9
set native-vlan 30
edit internal
set allowed-vlans 10,20,30
end
2. Configure system interfaces.:
config system interface
44 FortiSwitchOS-3.2.0
