When dude is installed onto a routerOS based router, there is no ablity to tell dude to use any other DNS server except the local router OS one.
I need to know if there was a way by using nat/mangle to redirect dude’s DNS requests to an external server, but leaving the routerOS DNS server/forwarder in tact. I have set up a seperate small DNS server that translates customers name to IP, its dynamic, and I need dude to look to this server for the DNS.
After a short review of your intended action, I do not believe this is possible. I did come up with an alternative though. Do not use the Dude hosting MT as a DNS server for your clients!
If the client DNS is set via DHCP, change the DHCP network settings to point to a different MT or DNS server. Once the clients renew their leases then you are free to change the DNS servers for the Dude MT to whatever you need. Alternately, you could also create a dst-nat rule, redirecting client DNS requests (by specifying the in- interface or src address range) to another server. The caveat here is that you cannot dst-nat out the same port the traffic arrived in on.
interface redirection example:
/ip fir nat add chain=dstnat in-interface=CLIENT_ETHER protocol=tcp dst-port=53 action=dst-nat to-addresses
=CLIENT_DNS to-ports=53
src-address redirection example:
/ip fir nat add chain=dstnat src-address=CLIENT_NET/MASK protocol=tcp dst-port=53 action=dst-nat to-addresses
=CLIENT_DNS to-ports=53
At first I was going to recommend dst-natting the loopback traffic destined for TCP/UDP 53, but that would also affect clients who use the Dude MT for DNS as it proxies the DNS requests to another remote server and would be subject to the same dst-nat rule.