randomly losing dns resolving ability

Question

I am seemingly randomly, but frequently (every few mins) losing my internet connectivity. The problem is not on the ADSL modem, but on the Linux router, that follows. A DNS server (bind) is running on the Linux router and when I can't access webpages , I realised, it is because I get no replies to my dns requests.

using the command tcpdump -ni eth1 -s 128 port 53

I send dns queries but don't get a reply. For example:

02:41:48.188398 IP 192.168.231.165.2898 > 128.63.2.53.53: 6525 A? ns2.denic.de. (30)
02:41:48.188480 IP 192.168.231.165.34131 > 128.63.2.53.53: 62058 AAAA? ns2.denic.de. (30)
02:41:48.188531 IP 192.168.231.165.44951 > 128.63.2.53.53: 60509 A? ns3.denic.de. (30)
02:41:48.188715 IP 192.168.231.165.57460 > 128.63.2.53.53: 22077 AAAA? ns3.denic.de. (30)
02:41:48.188884 IP 192.168.231.165.64112 > 128.63.2.53.53: 43050 AAAA? ns1.denic.de. (30)
02:41:49.680811 IP 192.168.231.165.51734 > 62.169.194.48.53: 34223+ AAAA? PLUS.GOOGLE.COM. (33)
02:41:49.833793 IP 192.168.231.165.34709 > 198.41.0.4.53: 18062 A? ns1.denic.de. (30)
02:41:49.834410 IP 192.168.231.165.55421 > 198.41.0.4.53: 37252 A? ns2.denic.de. (30)
02:41:49.834465 IP 192.168.231.165.32204 > 198.41.0.4.53: 9728 A? ns3.denic.de. (30)
02:41:49.834589 IP 192.168.231.165.36391 > 198.41.0.4.53: 25022 AAAA? ns2.denic.de. (30)
02:41:49.834726 IP 192.168.231.165.61125 > 198.41.0.4.53: 65397 AAAA? ns3.denic.de. (30)
02:41:49.834810 IP 192.168.231.165.39314 > 198.41.0.4.53: 52550 AAAA? ns1.denic.de. (30)
02:41:50.362847 IP 192.168.231.165.41937 > 62.169.194.48.53: 9737+ [1au] AAAA? CSI.GSTATIC.COM. (44)

IP address 192.168.231.165 is my side.

This question is following from this question, but apparently the problem occurs even when I am not downloading torrents.

since with torrents I could sort of avert the problem by limiting the download & upload rate of my torrents, I checked with iptraf the incoming / outgoing rate of packets.

When my connection works smoothly, the inc/outg are up to 12/24 kbps. when I can't access webpages (for the 2-4 mins duration) the rates are reduced abit compared to the above - but that could be an error on my part (due to limited observation sample).

I can't find a pattern as to why I don't get dns replies... my named.conf doesn't show anything in the logs. still there may be an error in my config as the queries.log is always empty. Do you have any suggestions?

Answer 1

You address (192.168.231.165) is simply not allowed to make a query to the server as it is not in the trusted ACL.

allow-query { trusted_subnets; };

acl trusted_subnets {
  local_nets;
  vpn_subnet;
  synthnassizer_subnet;
  dsa_office_subnet;
  skails_dns;
  synthnassizer_dns;
  dsa_dns;
  m2g_dns;
};

acl outbound_subnet {
  192.168.231.0/24;          // Your address is matched here
};

You can check this doc on allow-query option in config.