Load balancing among globally distributed servers

Load balancing : Load balancing among globally distributed servers

Global load balancing allows you to direct client queries for a specified domain to a pool that can contain both local and remote virtual servers. FortiADC redirects the client session based on server availability.

Before you configure global load distribution, first configure how FortiADC distributes traffic after it reaches the virtual server of each local cluster (see “Load balancing among local servers”).


	When the virtual server is located in a different country or continent than your servers, latency due to being physically located far away can impact response times. Because FortiADC only determines which virtual servers are available and not which ones are closest to the client, consider the possible impact on performance before you add the remote virtual servers to a global load balancing pool.

To configure global load balancing

1. Define each of your points of presence, including the servers in the pool, how FortiADC distributes the traffic, and the virtual server on the front end (“Load balancing among local servers”).

2. Go to Global Load Balance > Pool > Pool Config and select your pools of available virtual servers.

To add a local virtual server to the pool, select its name in Local VS Name. (You do not need to indicate its IP address; FortiADC finds it in the configuration file.)

If you add a remote virtual server (that is, one located at another point of presence and not part of this appliance’s configuration), specify its IP address and IPv4/IPv6 type.

3. Go to Global Load Balance > DNS > DNS Config and define the fully qualified domain name (FQDN). FortiADC responds to queries for this domain by sending clients to an available virtual server in the pool.

4. Contact your DNS provider and reconfigure your DNS records so that FortiADC’s public IP address is listed as the authoritative DNS server for this domain’s records.


	If a FortiGate or other firewall or NAT device is between clients and FortiADC, you may also need to reconfigure it to allow DNS queries to be sent to your FortiADC.

After DNS propagation (generally 24-48 hours), clients begin to query FortiADC for DNS resolution. FortiADC dynamically resolves the query to the IP of a virtual server, depending on currently available virtual servers in the pool.