Technical Tip: Implementing SD-WAN with 3 Internet Service Providers

Description

This article describes the implementation of SD-WAN with 3 Internet Service Providers (ISPs) using FortiGate.

The scenario applies when an existing SD-WAN deployment already contains two ISP connections and an additional ISP link must be integrated into the SD-WAN configuration.

Scope

FortiGate.

Solution

To implement SD-WAN with 3 ISPs, follow these steps:

1. Configure the third ISP interface on the FortiGate.
   

Navigate to: Network -> Interfaces.

Create or configure the physical or VLAN interface associated with the third ISP connection. Configure the required parameters: IP address, Administrative Access, Default Gateway, etc.

2. Add the new ISP interface to the SD-WAN configuration.

Navigate to: Network -> SD-WAN.

Under the SD-WAN Members, add the newly created WAN interface to the existing SD-WAN zone. Configure Interface priority, Gateway address and Cost.

3. Add the new ISP interface to the existing SD-WAN rules.

Navigate to: Network -> SD-WAN -> SD-WAN rules.

Edit the existing SD-WAN rules currently used by the deployment and add the newly configured ISP member to the rule members list.

4. Configure or update the Perfomance SLA health-checks.

Navigate to: Network -> SD-WAN -> Perfomance SLA.

If an existing Performance SLA is already configured for the current SD-WAN deployment, add the new ISP member as an additional participant in existing health-check object.

If no Performance SLA is configured, create a new health-check object to monitor WAN link availability, latency, jitter, and packet loss across all ISP members.

Example CLI configuration:

config health-check
    edit "health_check_name"
        set server 8.8.8.8
        set update-static-route enable
        set members 1 2 3
    end
end

Refer to the following articles for more information regarding Perfomance SLA configuration and SD-WAN troubleshooting: Defining performance SLA and Technical Tip: How to troubleshooting SD-WAN Performance SLA configured with FortiGuard SLA database.