0

192.168.1.1 is my router NetGear. It has 8.8.8.8 and 8.8.4.4 set as DNS. from windows:

nslookup google.com 192.168.1.1  // works OK

from ubuntu:

me@ubuntu:/etc/mail# dig @192.168.1.1 google.com +tcp
;; Connection to 192.168.1.1#53(192.168.1.1) for google.com failed: connection refused.

I think this shouldn't go on port 53, right? If yes, what can be the reason to dig translating my DNS query to asking NetGear on wrong port?

I cannot query 8.8.8.8:

dig @8.8.8.8 google.com

; <<>> DiG 9.9.2-P2 <<>> @8.8.8.8 google.com
; (1 server found)
;; global options: +cmd
;; connection timed out; no servers could be reached
root@ubuntuamd:/etc/mail# dig @8.8.8.8 google.com +tcp

however can with +tcp:

dig @8.8.8.8 google.com +tcp

; <<>> DiG 9.9.2-P2 <<>> @8.8.8.8 google.com +tcp
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 59432
;; flags: qr rd ra; QUERY: 1, ANSWER: 16, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;google.com.            IN  A

;; ANSWER SECTION:
google.com.     88  IN  A   46.28.247.93
google.com.     88  IN  A   46.28.247.119
//etc

;; Query time: 33 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Wed May  8 00:20:06 2013
;; MSG SIZE  rcvd: 295

at the end this: here 127.0.1.1 (dnsmasq right?) responds:

 dig  google.com

; <<>> DiG 9.9.2-P2 <<>> google.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 34747
;; flags: qr rd ra; QUERY: 1, ANSWER: 16, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;google.com.            IN  A

;; ANSWER SECTION:
google.com.     300 IN  A   208.117.224.29
//etc

;; Query time: 3 msec
;; SERVER: 127.0.1.1#53(127.0.1.1)
;; WHEN: Wed May  8 00:04:44 2013
;; MSG SIZE  rcvd: 284

nm tool:

me@ubuntu:/etc/mail# nm-tool | tail -n 8   IPv4 Settings:
    Address:         192.168.1.3
    Prefix:          24 (255.255.255.0)
    Gateway:         192.168.1.1

    DNS:             192.168.1.1
6
  • 3
    Port 53 is the DNS port. What makes you think it's wrong? May 7, 2013 at 22:06
  • but for listening. My query shouldn't go on routers 53 but some random port, isn't it? if it is OK then why it is refused?
    – 4pie0
    May 7, 2013 at 22:06
  • Your query should come from a random port (in a range) TO the designed server port of 53. May 7, 2013 at 22:15
  • Is your Ubuntu machine even connected to the network correctly? May 7, 2013 at 22:24
  • yes, I am on it currenntly
    – 4pie0
    May 7, 2013 at 22:26

3 Answers 3

6

Port 53 is indeed the port that a DNS server listens on for requests.

However, by default it's UDP port 53, and TCP port 53 is not often used.

Your dig and nslookup commands use UDP by default, but in your dig command you specified to use TCP with +tcp, and since the router is only listening on UDP, the request fails.

To resolve the issue, query with UDP by removing +tcp from your dig command.

3
  • no, this doesn't work
    – 4pie0
    May 7, 2013 at 22:21
  • Then provide the output. May 7, 2013 at 22:22
  • dig @192.168.1.1 google.com ; <<>> DiG 9.9.2-P2 <<>> 192.168.1.1 google.com ; (1 server found) ;; global options: +cmd ;; connection timed out; no servers could be reached
    – 4pie0
    May 7, 2013 at 22:23
1

DNS runs on Port 53.

Port 53 is the IANA assigned port for DNS.

dig does a DNS lookup. nslookup does a DNS lookup. Thus they both use Port 53.

As to your real question, which is:

then why it is refused?

Well, that could be for any number of reasons. Maybe your Ubuntu computer is on a different network. Maybe its network cable is unplugged. Maybe you have firewall rules blocking outbound DNS except to some specific IP addresses.

Is there a specific problem you're trying to solve by doing this dig command?

6
  • yes, I cannot query 8.8.8.8 directly
    – 4pie0
    May 7, 2013 at 22:19
  • please see the update
    – 4pie0
    May 7, 2013 at 22:20
  • Try again without the +tcp May 7, 2013 at 22:22
  • @DarthAndroid have you any idea why doesn't work without +tcp? on windows it works without +tcp
    – 4pie0
    May 7, 2013 at 22:35
  • 2
    @restart.localhost.localdomain The default DNS port is 53 UDP. Sometimes, DNS servers simply aren't listening for a TCP connection because they're expecting UDP. May 7, 2013 at 22:43
1

You should install bind and use 127.0.1.1. This might help and resolve your problems.

0

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .