If a VPN is set up in the company network via SSL VPN client "SecuExtender", the DNS resolution for internal servers only works with the whole FQDN:
ping server.contoso.local works
ping server is not working
This is due to a missing DNS suffix.
For Windows
In the settings of the SecuExtender network adapter (TAP-Windows Adapter for Zyxel SecuExtender)
Mark internal protocol version 4 -> Properties
Advanced
Click the DNS tab and enter DNS suffix (contoso.local)
Check again if the DNS resolution works.
In MAC OS.
open a terminal and enter the following commands
sudo mkdir /etc/resolver
sudo touch /etc/resolver/viscosity
sudo nano /etc/resolver/viscosity
enter the following content:
domain contoso.local
search contoso.local
nameserver X.X.X.X
nameserver X.X.X.X
exit and save the document with control+x and y
Now the Ping to the server should work.