I'm having the strangest issue with my DIR-855LA1, Firmware: 1.09 Tue 27 Aug 2013. I am simply not receiving any requests from my network to my external DNS servers. I have specified a Dynamic IP internet connection type (DHCP) under "Manual Internet Connection" on the Internet setup page, with a custom Primary and Secondary DNS server, both of which I own and both of which are located outside of the my network. I can see in the dnsmasq logs on my servers that I do not receive requests; despite having the relevant UDP / TCP ports open for DNS queries, etc.
My DIR-850LA is bridged to a WAN gateway modem that is provided by my ISP, if that is relevant.
After much experimentation, it seems that the only way to get my DIR-850LA to query my external DNS servers is to specify the connection type as Static, along with the IP address issued by my bridged WAN connection, the gateway IP address and my two DNS servers. The MTU is set at 1494. I'd set it to 1474 at one point, but that completely killed the internet connection. I've also muddled around with the "Enable DNS Relay" feature as well, and am not 100% convinced that it does much of anything :p However, this solution is unreliable as all DNS resolution fails after a day or so.
Am I doing something wrong here? Can I not specify custom DNS Servers with a Dynamic IP connection type?
If I am missing any relevant information, please let me know!
Thanks in advance.