The NetScaler hybrid and multi-cloud global server load balancing (GSLB) solution enables customers to distribute application traffic across multiple data centers in hybrid clouds, multiple clouds, and on premises. The NetScaler GSLB solution supports various load balancing solutions, such as the NetScaler load balancer, Elastic Load Balancing (ELB) for Amazon Web Services (AWS), and other third-party load balancers. Also, the GSLB solution performs global load balancing even if the GSLB and load balancing layers are independently managed.
In cloud deployments, users are given a domain name as a reference when accessing the load balancing solution for management purposes. It is recommended that external entities do not use the IP addresses that these domain names resolve to. Also, the load balancing layers scale up or down based on the load, and the IP addresses are not guaranteed to be static. Therefore, it is recommended to use the domain name to refer to the load balancing endpoints instead of IP addresses. This requires the GSLB services to be referred using the domain name instead of IP addresses and it must consume all the IP addresses returned for the load balancing layer domain name and have a representation for the same in GSLB.
To use domain names instead of IP addresses when referring to the load balancing endpoints, you can use the domain name based service groups for GSLB.

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Instructions

1. Add a name server with the DNS gateway IP address where the GSLB node is added. This must be created in each datacenter.
2. Add the domain based server to each NetScaler appliance using the FQDN. Navigate to Traffic Management > Load Balancing > Servers > Add.

4. Add the GSLB Autoscale Service Group. In the GUI, navigate to Traffic Management > GSLB > Service Groups > Add.

Or issue the command:
add gslb serviceGroup dublin_sg HTTP -autoScale DNS -siteName Dublin
 
5. Bind each server to the service group:
bind gslb serviceGroup dublin_sg dublin_server 80

The NetScaler provides statistics for each GSLB Service Group Member:

If the NetScaler is not able to reach each GSLB Service Group Member, they will either be listed as in a DOWN state or not listed at all:

6. Bind the GSLB service group to the GSLB virtual server


Additional Info:

• The NetScaler appliance has two built-in monitors that monitor TCP-based applications; tcp-default and ping-default. The tcp-default monitor is bound to all TCP services and the ping-default monitor is bound to all non-TCP services. The built-in monitors are bound by default to the GSLB service groups. However, it is recommended to bind an application specific monitor to the GSLB service groups.
• For a load balancing domain, the IP address that is returned in the DNS response is generally the public IP address. The private IP address cannot be applied dynamically when the load balancing domain is resolved. Therefore, public IP port and private IP port for the GSLB domain name based autoscale service groups IP port bindings are the same and these parameters cannot be set explicitly for the domain name based autoscale service groups.
• Site persistence, DNS views, and clustering is not supported for GSLB service groups.