If you use a Domain Name System (DNS) record to route user traffic in your data centers, the DNS record should point to a load balancer in the primary data center under normal operating situations.

If the primary data center becomes unavailable, the DNS record should be updated to point to the load balancer in the secondary data center.

When the primary data center becomes available again, the DNS record should be updated to point to the load balancer in the primary data center.

Mobile SSO for iOS Authentication

If you are using Mobile SSO for iOS authentication, update both the A and AAAA DNS entries to point to the load balancer in the secondary data center. For example: 

idm.example.com.   1800 IN  AAAA         ::ffff:1.2.3.4
idm.example.com.   1800 IN  A            1.2.3.4
Note: If you are using the hybrid KDC feature, this is not required.

Setting Time To Live in DNS Record

The time to live (TTL) setting determines how long before DNS related information is refreshed in the cache. For a seamless failover of Horizon desktops and applications, make sure that the time to live (TTL) setting on the DNS records is short. If the TTL setting is set too long, users might not be able to access their Horizon desktops and applications immediately after failover. To enable quick refresh of the DNS, set the DNS TTL to 30 seconds.