Step by step guide to configure Forward Lookup Zone for SharePoint Apps
Navigate to Server Manager ->Tools, and then click DNS.
In DNS Manager, right-click Forward Lookup Zones, and then click New Zone
In the New Zone Wizard, click Next.
Primary zone, and then click Next.
In the Active Directory Zone Replication Scope page, select to all DNS servers in this domain
In the Zone name box type the name for your new app domain name
Please select below options on the Dynamic Update
On the Completing the New Zone Wizard click Finish.
Now Once App Domain is created successfully lets link it to SharePoint Server
Link the App Domain to the SharePoint Server
Under Forward Lookup Zones, right-click the new app domain name, and then click New Alias (CNAME).
Enter * As Alias name and Foe Fully qualified domain name (FQDN) , click Browse and navigate to the Forward Lookup Zone for the domain that hosts the SharePoint sites and then navigate to the record that points to the server that hosts the SharePoint site.
To verify domain name
Navigate to Start -> Command Prompt
and Type ping followed by a sub domain of the domain that you created, and then press ENTER