Symptoms
When installing K2 for SharePoint 4.6.9. K2 for SharePoint Setup Manager Configuration Analysis reports failure for “Ping SharePoint App Domain” task.
Diagnoses
In most of the cases, this error means that there is an issue with DNS entry for SharePoint app domain. SharePoint 2013 Apps must be enabled for the K2 for SharePoint App to work and setup manager does number of checks to verify this including ping of SharePoint app domain.
Please refer to K2 documentation for further details on this:
Deploy the K2 for SharePoint App to the App Catalog (see App Domain Tasks section)
Resolution
To address this issue you have to verify that correct DNS entry was created for your SharePoint App Domain. To enable SharePoint 2013 apps you have to create app domain in DNS to host your apps. Each installation of an app has its own unique URL within the app domain. You either can create a new domain for your apps or a subdomain. For improved security (according to Microsoft documentation), SharePoint 2013 app domain name should not be a subdomain of the domain that hosts the SharePoint sites.
Please refer to the following Microsoft documentation on configuring SharePoint 2013 app domain:
Configure an environment for apps for SharePoint (SharePoint 2013)
Plan for apps for SharePoint 2013
For step by step guidance on how to perform DNS specific configuration you may refer to the following blog post:
http://www.sharepointchick.com/archive/2012/07/29/setting-up-your-app-domain-for-sharepoint-2013.aspx
In short, you just have to create new DNS zone (domain), with an Alias (CNAME) wildcard entry. This wildcard entry should use “*” as an alias name and either reference domain of your SharePoint environment (single SharePoint server scenarios) or DNS record of the web server (for multi-server deployments) as FQDN for target host. In case of multi-server deployments, you reference to the DNS A record either for the web server, or to the DNS record for the primary cluster address for NLB environments.
Above-mentioned post also consider less preferable sub domain option, which boils down to creating the same wild card entry for your apps in existing domain.
