When connected to a VPN the remote site can be accessed by IP address but not via hostname?

Scenario 1:

By default “NetBIOS over TCP/IP” is disabled for the VPN connection created by Smart VPN client. When it is enabled the whole vpn network cannot be accessed.

scenario 2:  Try to use DNS forwarding

see this Url :  https://www.draytek.com/support/knowledge-base/5067