Multiple ISP connections at each point of presence helps to guarantee the availability of your services by building redundancy, but you can also configure your FortiADC so that you can use it to increase available bandwidth, optimize costs, and reduce latency: instead of switching to use the secondary ISP only when the primary ISP link fails, you can distribute traffic among available ISP links, weighting distribution if necessary to avoid charges for excess bandwidth.

Similar to global server load balancing, link load balancing avoids the need for failover via BGP by using DNS-based load balancing and gateway beacons instead. However, link load balancing adds the capability of clients reaching each of your points of presence through multiple paths.

In most cases, you configure link load balancing for both outgoing and incoming traffic, unless a server is acting as a client (for example, a server that replicates directories or propagates DNS records). In this case, since the server that is acting as a client to another server does not have incoming traffic from many clients that must be balanced, you could configure link load balancing for outgoing traffic only.