When I refresh a device that correctly has the SNMP Sysname used as the display name (Displayname),  the display name is changed to the DNS returned FQDN.  

When a device is initially added using a New Scan, the option to "Use Sysname" as the Displayname is selected, this works as expected and the displayname is set by pulling the sysname from the device (if available via a valid SNMP Credential).   However,  when refreshing,  the default for setting the Displayname (based on the discovery service configuration file) is to use the "hostname" or FQDN.  There is no option during a refresh to request a different result.   Because of that,  the Displayname will change to FQDN.

This defect was resolved in WhatsUp Gold version 24.0.2 by adding a new key to the discover service configuration file (DiscoveryService.exe.config) that allows a change to the default behavior for Displayname.  

To set the Displayname to use the SNMP return Sysname by default, please do the following:

1) On the WhatsUp Gold server navigate to the Whatsup Gold installation directory (c:\Program Files (x86)\Ipswitch\Whatsup, by default).

2) Find the file discoveryservice.exe.config file and open the file using Notepad.

3) Find the following line in the file:    

<!--<add key="defaultDisplayNamePreferences" value="HDNSdVvChsnI"/>-->

4) Replace that line with the following:    

<add key="defaultDisplayNamePreferences" value="SHDNdVvChsnI"/>

5) Save the file

6) In the WhatsUp Gold web console go to Settings / System Services.

7) Under System Services find the discoveryservice.exe and select it.  Click the option to restart the service.

After the discovery service restarts,  the default behavior for discovered devices will be to use the Sysname as the Displayname, if available.