DNS problem with LTSP server on OPT

[revmarkp]

I have a ubuntu 16.04 server with static IP (192.168.14.10) on an OPT interface (192.168.14.1) that can't resolve DNS. (The server is a VE machine on Proxmox)

I am not running DHCP on this static IP OPT, as I setup the LTSP server to be the DHCP server for the LTSP clients. Weirdly the LTSP clients DNS resolution is fine, but somethings gone awry with the sever they work under. Someone suggested this might be a squid complication, which I was testing out, but i turned that off, and for good measure have now uninstalled it.

Help for a relative noob appreciated.

Some screen shots that might be helpful:

route from the offending server:

/etc/network/interfaces of server:

Is this 'server' showing in dig the correct IP?

pfSense 2.3.5 (i386):

If it's relevant I setup my LTSP server using this guidance:
http://www.havetheknowhow.com/Configure-the-server/Install-LTSP.html
It's a single NIC setup, unlike some that use two.