DNS Resolution

A

Antonino89

Member
Jul 13, 2017
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Hi guys,,

currently i have a problem with all of my server:

I can ping public IP adress but i'm not able to ping their hostname.

ping 8.8.8.8 is OK
ping Google.it is NOT OK.

my resolv.conf :

root@Server1:/etc# more resolv.conf

search proxmox
nameserver 8.8.8.8
nameserver 8.8.4.4
nameserver 192.168.100.1

Any suggestions?

Thanks :)

 
It's time to dig then ;)
Code: 
$ dig google.it   

; <<>> DiG 9.10.3-P4-Debian <<>> google.it
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 9377
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4000
;; QUESTION SECTION:
;google.it.            IN    A

;; ANSWER SECTION:
google.it.        133    IN    A    172.217.21.227

;; Query time: 1 msec
;; SERVER: 192.168.2.121#53(192.168.2.121)
;; WHEN: Wed Aug 09 17:13:36 CEST 2017
;; MSG SIZE  rcvd: 54
It tells you where you received the answer from in the SERVER line. If you don't get an answer from one of your nameservers you can force using them with
Code: 
$ dig @8.8.8.8 google.it
Also I assume you already rebooted after entering that config or, at the very least, restarted the network.
 
Yes, reboot was done.


root@Server1:~# dig google.it

; <<>> DiG 9.10.3-P4-Debian <<>> google.it
;; global options: +cmd
;; connection timed out; no servers could be reached
root@Server1:~# dig @8.8.8.8 google.it

; <<>> DiG 9.10.3-P4-Debian <<>> @8.8.8.8 google.it
; (1 server found)
;; global options: +cmd
;; connection timed out; no servers could be reached


Problem, still remain...
 
Can you query the local DNS server (assuming you have at least a local DNS cache available)?
Is there a router or firewall on the network that might block outgoing DNS requests?
 
pabernethy said:
Can you query the local DNS server (assuming you have at least a local DNS cache available)?
Is there a router or firewall on the network that might block outgoing DNS requests?
Click to expand...


root@Server1:~# ping 10.216.110.108 <------ Local DNS
PING 10.216.110.108 (10.216.110.108) 56(84) bytes of data.
64 bytes from 10.216.110.108: icmp_seq=1 ttl=127 time=2.54 ms
64 bytes from 10.216.110.108: icmp_seq=2 ttl=127 time=1.24 ms
64 bytes from 10.216.110.108: icmp_seq=3 ttl=127 time=1.05 ms
64 bytes from 10.216.110.108: icmp_seq=4 ttl=127 time=1.01 ms
64 bytes from 10.216.110.108: icmp_seq=5 ttl=127 time=1.50 ms
^@64 bytes from 10.216.110.108: icmp_seq=6 ttl=127 time=1.18 ms

64 bytes from 10.216.110.108: icmp_seq=7 ttl=127 time=1.14 ms

64 bytes from 10.216.110.108: icmp_seq=8 ttl=127 time=1.10 ms
^Z
[1]+ Stopped ping 10.216.110.108


root@Server1:~# dig @10.216.110.108 google.it

; <<>> DiG 9.10.3-P4-Debian <<>> @10.216.110.108 google.it
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 9690
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4000
;; QUESTION SECTION:
;google.it. IN A

;; ANSWER SECTION:
google.it. 299 IN A 172.217.16.163

;; Query time: 27 msec
;; SERVER: 10.216.110.108#53(10.216.110.108)
;; WHEN: Thu Aug 10 10:19:28 CEST 2017
;; MSG SIZE rcvd: 54
 
Looks like your firewall is blocking outgoing DNS requests. So either talk to the network administrator, if you absolutely need to use external DNS. Or just use the local DNS.
 
I had a similar problem. Check on your firewall that you have traffic permissions up to 53 TCP and UDP ports. There is most likely no UDP.
 
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