Load balancing : Load balancing among links
Load balancing among links
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.
Link load balancing should typically be configured for both outgoing and incoming traffic, unless a server is acting as a client, such as when replicating directories or propagating 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.
By default, the link load balancing menu is hidden. To show it, see “Menu Settings”.
To configure load balancing among links
1. Define each of your points of presence, including the servers in the pool, how the traffic will be distributed, and the virtual server on the front end (“Load balancing among local servers”).
2. Configure the health check that will be used to determine the availability of each ISP link (“Monitoring link health or availability”).
3. Configure the gateway for each ISP link, and indicate how FortiADC should distribute outgoing traffic among available links (“Routing outbound traffic through a link”).
4. If you also want to load balance incoming traffic, configure the pool of virtual servers, each having an IP on one of your ISP links and a gateway for DNS replies, then define the domain name that will be load balanced over available links (“Link load balancing for inbound traffic”).