Follow the below steps to configure the GSLB service for the above scenario:
Configure GSLB pool member using the IP address option.
Specify the FQDN of multi-VIPs. As shown in the screenshot below, the FQDN is either aws-vs.demo.awsavi.net or aws-vs-east.demo.awsavi.net
As shown in the above screenshot, the pool member is configured with a FQDN.
The FQDN is resolved to an IP address on the Controller.
The DNS virtual service monitors the health of the resolved address while it returns the CNAME in its response.
If the user has configured an IP address, then the IP address will get overwritten whenever a periodic FQDN refresh is done by the Controller.
Only one of the IPs, not all is monitored. Either the NSX Advanced Load Balancer Controller or AWS withdraws IP addresses/members that are not up.
A client sends a request to access avi.app.gslb.com.
The request lands on NSX Advanced Load Balancer DNS virtual service, which identifies the most optimal pool member. In this case, either aws-vs.demo.awsavi.net or aws-vs-east.demo.awsavi.net (pool members) is selected, based on the GSLB method specified.
The NSX Advanced Load Balancer DNS virtual service responds to the client with a CNAME in the response.
The same CNAME is sent to the client.
Once the client gets the CNAME, the client sends another DNS query for resolution of the CNAME, based on the DNS server configuration. AWS may be configured as authoritative for subdomain demo.awsavi.net, NSX Advanced Load Balancer may be authoritative, or DNS settings may be configured in some other way.
The CNAME gets resolved to one of the IP addresses of the individual VIPs (based on the DNS server used by the client, either Route 53 or NSX Advanced Load Balancer DNS).
In both cases, these FQDNs (aws-vs.demo.awsavi.net or aws-vs-east.demo.awsavi.net) of multi-VIP virtual service get automatically recorded/registered in the DNS as A records pointing to individual VIPs. For example - if Route 53 is used as the DNS while deploying the cloud, then the FQDNs get registered on Route 53 as shown below.
If NSX Advanced Load Balancer DNS is used instead, then the FQDNs get registered within NSX Advanced Load Balancer in a similar way.