Constant DNS querys

Hi all,
I have a problem with my mt router. I have a router from my ISP. (inet IP 192.168.0.0/24) and I have my MT router (inet IP 192.168.1.0/24 it’s a NATted network the external IP is 192.168.0.2). What’s my problem is: last days I see a Negative DNS cache. I started to log all dns querys and what i seen: To this negative cached IP lets my router send every 10 s a query and get the answer dns name does not exist. What my question is. Is it normal that my router sends every 10 sec a dns query to an IP address?
Thanks for your help in advance, and sorry for my english, Im from Hungary