I have OpenVPN server installed on ASUS router with Advanced Tomato and on QNAP NAS. Both in the same LAN. Both units have installed DNSMASQ, and contents of DNS definitions are synced so practically are the same. Of course except some particular unit dependent parameters.
I can without problem login over OpenVPN to Asus and to NAS.
So my problem is like this.
When I log in over OpenVPN to Asus, it is possible to use mnemonic names of other Ethernet nodes in LAN, so DNSMASQ bind to LAN interface of Asus works properly.
But when I log in to QNAP NAS, it possible to reach particular Ethernet node inside LAN only using IP address. So it is not possible to use DNSMASQ installed on NAS. On NAS DNSMASQ is bind to LAN (bride) interface.
NAS is equipped in 4 Ethernet ports configured as switch bridged to internal Ethernet interface.
DNSMASQ works properly because if I query DNS server on NAS about IP address of particular Ethernet node in LAN from device connected to the same LAN it answer properly.
But why it does not responds on query from OpenVPN connection?

Openvpn communicates on port UDP 1194. You must open the correct ports to communicate.

My units are configured as follows:
ASUS - port 1195/UDP - and it works correctly
QNAP - port 1194/TCP - and it does not work properly. That means I can connect, but Ethernet nodes inside LAN can be reached only by using IP address.
But when I set on client for QNAP connection, DNS as a address of Asus, it works correctly.
QNAP does not have any firewall activated.
On the router both TCP and UDP protocols are open for port 1194.
So, what the problem is?