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#1 2010-08-20 02:38:43

flay0303
Member
Registered: 2010-01-26
Posts: 29

[SOLVED]DNS resolve problem

Today,I found a stranger querstion,I can ping DNS server,but can not resolve the domain。

$cat /etc/resolv.conf 
# Generated by NetworkManager
nameserver 202.103.6.46
nameserver 202.103.24.68
nameserver 202.103.44.150

$ping 202.103.6.46
PING 202.103.6.46 (202.103.6.46) 56(84) bytes of data.
64 bytes from 202.103.6.46: icmp_seq=1 ttl=249 time=2.47 ms
64 bytes from 202.103.6.46: icmp_seq=2 ttl=249 time=4.26 ms
64 bytes from 202.103.6.46: icmp_seq=3 ttl=249 time=4.00 ms
64 bytes from 202.103.6.46: icmp_seq=4 ttl=249 time=3.00 ms
64 bytes from 202.103.6.46: icmp_seq=5 ttl=249 time=6.98 ms
64 bytes from 202.103.6.46: icmp_seq=6 ttl=249 time=8.27 ms
64 bytes from 202.103.6.46: icmp_seq=7 ttl=249 time=1.53 ms
64 bytes from 202.103.6.46: icmp_seq=8 ttl=249 time=4.62 ms
^C
--- 202.103.6.46 ping statistics ---
8 packets transmitted, 8 received, 0% packet loss, time 7009ms
rtt min/avg/max/mdev = 1.534/4.393/8.270/2.115 ms

now,I use Google public DNS 8.8.8.8
what's the matter?
How to fix this?

Last edited by flay0303 (2010-08-20 11:23:35)

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#2 2010-08-20 03:11:42

fukawi2
Ex-Administratorino
From: .vic.au
Registered: 2007-09-28
Posts: 6,224
Website

Re: [SOLVED]DNS resolve problem

flay0303 wrote:

now,I use Google public DNS 8.8.8.8

No you don't:

flay0303 wrote:
$cat /etc/resolv.conf 
# Generated by NetworkManager
nameserver 202.103.6.46
nameserver 202.103.24.68
nameserver 202.103.44.150

I'm guessing the 3 nameservers listed in your resolv.conf aren't responding. Install dnsutils and check the output of `dig google.com`

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BlueHackers // fscanary // resticctl

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#3 2010-08-20 04:23:22

flay0303
Member
Registered: 2010-01-26
Posts: 29

Re: [SOLVED]DNS resolve problem

$ cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 202.103.6.46
nameserver 202.103.24.68
nameserver 202.103.44.150

$dig google.com

; <<>> DiG 9.7.1-P2 <<>> google.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: REFUSED, id: 489
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0

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

;; Query time: 9 msec
;; SERVER: 202.103.6.46#53(202.103.6.46)
;; WHEN: Fri Aug 20 12:17:14 2010
;; MSG SIZE  rcvd: 28


$ nslookup google.com
Server:        202.103.6.46
Address:    202.103.6.46#53

** server can't find google.com: REFUSED
$cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 8.8.8.8

$dig google.com

; <<>> DiG 9.7.1-P2 <<>> google.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 22986
;; flags: qr rd ra; QUERY: 1, ANSWER: 6, AUTHORITY: 0, ADDITIONAL: 0

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

;; ANSWER SECTION:
google.com.        300    IN    A    74.125.153.99
google.com.        300    IN    A    74.125.153.103
google.com.        300    IN    A    74.125.153.106
google.com.        300    IN    A    74.125.153.147
google.com.        300    IN    A    74.125.153.104
google.com.        300    IN    A    74.125.153.105

;; Query time: 112 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Fri Aug 20 12:20:39 2010
;; MSG SIZE  rcvd: 124

$ nslookup google.com
Server:        8.8.8.8
Address:    8.8.8.8#53

Non-authoritative answer:
Name:    google.com
Address: 74.125.153.99
Name:    google.com
Address: 74.125.153.103
Name:    google.com
Address: 74.125.153.106
Name:    google.com
Address: 74.125.153.147
Name:    google.com
Address: 74.125.153.104
Name:    google.com
Address: 74.125.153.105
$ping 202.103.6.46
PING 202.103.6.46 (202.103.6.46) 56(84) bytes of data.
64 bytes from 202.103.6.46: icmp_seq=1 ttl=249 time=76.7 ms
64 bytes from 202.103.6.46: icmp_seq=2 ttl=249 time=60.9 ms
64 bytes from 202.103.6.46: icmp_seq=3 ttl=249 time=41.9 ms
64 bytes from 202.103.6.46: icmp_seq=4 ttl=249 time=2.53 ms
^C
--- 202.103.6.46 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3004ms
rtt min/avg/max/mdev = 2.535/45.574/76.768/27.731 ms

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#4 2010-08-20 07:00:23

fukawi2
Ex-Administratorino
From: .vic.au
Registered: 2007-09-28
Posts: 6,224
Website

Re: [SOLVED]DNS resolve problem

Well that confirms it -- the 3 nameservers in resolv.conf are screwed. Don't use them wink

(At least 202.103.6.46 is, the other 2 might be OK. Remove .46 and retest)

Are you familiar with our Forum Rules, and How To Ask Questions The Smart Way?

BlueHackers // fscanary // resticctl

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#5 2010-08-20 09:19:25

flay0303
Member
Registered: 2010-01-26
Posts: 29

Re: [SOLVED]DNS resolve problem

fukawi2 wrote:

Well that confirms it -- the 3 nameservers in resolv.conf are screwed. Don't use them wink

(At least 202.103.6.46 is, the other 2 might be OK. Remove .46 and retest)

thanks,you are right!
I use 202.103.24.68,it's OK.
but，Why it does not automatically switch the next DNS server?

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#6 2010-08-20 09:57:49

fukawi2
Ex-Administratorino
From: .vic.au
Registered: 2007-09-28
Posts: 6,224
Website

Re: [SOLVED]DNS resolve problem

Because the first server answers, rather than timeout. IIRC, it will only try the next server if the current one doesn't respond, regardless of whether the response is good or bad.

Are you familiar with our Forum Rules, and How To Ask Questions The Smart Way?

BlueHackers // fscanary // resticctl

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#7 2010-08-20 11:22:20

flay0303
Member
Registered: 2010-01-26
Posts: 29

Re: [SOLVED]DNS resolve problem

fukawi2 wrote:

Because the first server answers, rather than timeout. IIRC, it will only try the next server if the current one doesn't respond, regardless of whether the response is good or bad.

Thank you very much!

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