For a while now, I have been using the DNS Proxy feature of the UTM5 so that the PCs that connect to my network using DHCP can get the UTM's LAN IP as their DNS server which then acts as a proxy for my ISP's DNS servers. This all works fine.
I am now introducing a DNS server to my LAN for internal name resolution only. So I have set it up to forward any DNS requests for external name resolution to my ISP's DNS servers and switched off the DNS Proxy feature in the UTM5. In my UTM5's LAN / DHCP settings I have included my internal DNS server's IP so that DHCP clients get this automatically. To my mind this should all work.
However, I am finding that web pages now load much more slowly. Also, if I go back to my original LAN / DHCP settings with DNS Proxy selected, but put the internal DNS server's IP manually in a PC's NIC setting, performance goes back to normal and internal name resolution still works.
So, I am a bit confused. Do I still need to run the DNS proxy for my setup?
