SD-WAN interface data usage issue. Weight set 100:0

[ThatDudeFromNZ]

Hi,

I have a FortiGate60E with two internet connections: Primary:Wan1 and Backup:Wan2; setup SD-WAN with these 2 interfaces for redundancy. 

The backup internet connection has a 100GB data cap which was nearly hit last month, I adjusted the Weight to 100:0 a few days back and it's still consuming huge amounts of data. Attached a screenshot, left side is 3 days and right side today which has 20GB increased received data.

Any ideas where I'm going wrong? 

[Philippe_Gagne]

Hi,

I suggest you to use "SD-Wan Rules" to force traffic on wan1, weight is not mandatory for the SD-Wan feature, I consider it as a "suggestion" where to send traffic. I have a lot of customers who use cellular modem as backup link, with SD-Wan rules, only the monitoring pings are sent to them. 

For your information, when you create a rule that send everything to a specific member of the SD-Wan, when this member failed, rules pointing to it will not matche and the failover will occur.

Regards,

Philippe

[hubertzw]

"The FortiGate uses the volume weight that you assign to each interface to calculate a percentage of the total bandwidth that’s allowed to go through each interface. The FortiGate then distributes the bandwidth between the interfaces accordingly."

I think you need Spillover in your case.

Source: https://help.fortinet.com/fos60hlp/60/Content/FortiOS/fortigate-networking/SD-WAN/SD-WAN_load_balanc...