| Description | This article describes how to do ECMP load balancing with SD-WAN configuration. |
| Scope | FortiGate. |
| Solution |
Using SD-WAN load balance of traffic can be done by navigating to SD-WAN -> SD-WAN Rules ->Implicit Rule. There are 5 ways to load balance the traffic as shown below.
The traffic will hit the implicit rule only when traffic does not match any of the rules in the SD-WAN rules or if no rules are configured as shown below.
In this case, create a static route for the same destination with the same administrative distance and priority as shown below, the traffic will match the longest prefix even though there is an SD-WAN interface, and load balancing will happen between the two interfaces PORT1 and PORT2.
The routing table will look as shown below. Here, the '8.8.8.8' prefix length is 32 and the one with the default route is '0', so the table will consider one with a 32 prefix length by default.
Find the active routes for the specific destination.
Note:
config system sdwan set load-balance-mode measured-volume-based end
The measured-volume-based and SD-WAN load-balancing mode settings found under the system sub-menu are solely applicable to the implicit rule. Volume-based load balance is not available in the custom SD-WAN rules.
To set a load balance strategy in the custom rules use the following commands:
config system sdwan config service edit <id> set load-balance enable set hash-mode round-robin/source-ip-based/source-dest-ip- based/inbandwidth/outbandwidth/bibandwidth end end end
If the SD-WAN rules are required to be configured the load balance option can be found for the 'Manual' and 'Lowest Cost(SLA)' interface selection strategy with all the hash modes mentioned above.
Related articles: Implicit rules - FortiGate administration guide Configuring SD-WAN load balancing - FortiGate handbook Technical Tip: ECMP Load balancing algorithms for IPv4 and IPv6 |
