FortiADC
FortiADC enhances the scalability, performance, and security of your applications whether they are hosted on premises or in the cloud.
guptas
Staff
Staff
Article Id 296888
Description This article describes how to configure one of the ISPs as a backup ISP in LLB and if all active LLB links go down then only Backup will serve the user traffic. 
Scope FortiADC.
Solution

Consider multiple ISP links in LLB under Link Group, if it is not desired to use one LLB link for the user request and want to set this link as a backup Link only, only serve the request when all other LLB link goes down then it is possible to configure the Backup option as below:

 

Link Load balance -> Link Group -> Link Member -> Create new.  

 

LLB-Bakup.png

 

Related document:

Configuring a link group