You have at least two datacenters running the same application. The primary datacenter is always active. In case of failure/disaster the secondary/backup datacenter must kick in taking control and providing access to your application (disaster recovery)
Your application is mapped on a well-defined hostname (ie. www.myapplication.com)
On the primary datacenter www.myapplication.com is running on IP a.b.c.d. One the secondary/backup datacenter www.myapplication.com is running on IP x.y.z.t
You need your clients traffic to be sent to the primary datacenter and, only in case of unavailability, be transparently sent to the secondary/backup datacenter
Select under which one of the available domains (gslb.us, gslb.info, …) you want to create your geohost. You can choose the domain you prefer, this is purely a “cosmetic” choice. Let’s choose myapplication.gslb.info
Create your geohost: a geohost is the FQDN (Fully Qualified Domain Name) that your authoritative DNS will use as a CNAME for your application hostname (ie. www.myapplication.com). Select “Priority” as your balancing algorithm. This will enable active-standby distribution of incoming traffic towards your datacenters.
Define the first target: the target’s IP address is a.b.c.d and its priority must be 1
Select checks to be performed on the first target
Define the second target: the target’s IP address is x.y.z.t and its priority must be any number higher than 1. This allows the “priority” balancing algorithm to handle active-standby.
Select checks to be performed on the second target
Configure your authoritative DNS to use a CNAME record to have www.myapplication.com point to myapplication.gslb.info
