The ADSL offer of my ISP OVH includes lending an antiquated TG784n. For the local machines that registers to its DHCP, it gives its own IP (192.168.1.254) as DNS server, and recently this DNS stopped answering (=> timeout) to requests for domain names whose associated IP is a private IP (192.168.x.y, 10.x.y.z). The DNS servers of my ISP resolved them correctly.

Resolution: I don’t know the root cause, by I could solve it this way

• Telnet on the router: telnet 192.168.1.254
• Enter your router login/password if any.
• Enter the command: dns server config filter=disabled
• Note that this command did not solve the issue: dns server config WANDownSpoofing=disabled

When the filtering of these requests is done, their count can be observed with this command:

{Administrator}=>dns server debug stats
[…bla bla bla…]
Spurious answers                 :       189