DNS Resolution Problem
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- Posts: 4
- Joined: 2007/06/05 09:57:12
- Location: Jakarta, Indonesia
DNS Resolution Problem
Hi All , my computer can not resolve address from DNS server.
I use CentOS 4.4. This computer used as Web Server and DHCP server, no DNS service installed on this computer.
For DNS server I use my ISP DNS server. Other network function work normal
Here some output when I try to ping centos.org server
[raiden@shiro ~]$ ping centos.org
ping: unknown host centos.org
[raiden@shiro ~]$ nslookup centos.org
Server: 202.169.33.220
Address: 202.169.33.220#53
Non-authoritative answer:
Name: centos.org
Address: 72.232.194.162
[raiden@shiro ~]$ ping 72.232.194.162
PING 72.232.194.162 (72.232.194.162) 56(84) bytes of data.
64 bytes from 72.232.194.162: icmp_seq=0 ttl=46 time=258 ms
64 bytes from 72.232.194.162: icmp_seq=1 ttl=42 time=252 ms
64 bytes from 72.232.194.162: icmp_seq=2 ttl=46 time=259 ms
--- 72.232.194.162 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2002ms
rtt min/avg/max/mdev = 252.526/256.884/259.202/3.111 ms, pipe 2
Thanks for the help...
8-)
I use CentOS 4.4. This computer used as Web Server and DHCP server, no DNS service installed on this computer.
For DNS server I use my ISP DNS server. Other network function work normal
Here some output when I try to ping centos.org server
[raiden@shiro ~]$ ping centos.org
ping: unknown host centos.org
[raiden@shiro ~]$ nslookup centos.org
Server: 202.169.33.220
Address: 202.169.33.220#53
Non-authoritative answer:
Name: centos.org
Address: 72.232.194.162
[raiden@shiro ~]$ ping 72.232.194.162
PING 72.232.194.162 (72.232.194.162) 56(84) bytes of data.
64 bytes from 72.232.194.162: icmp_seq=0 ttl=46 time=258 ms
64 bytes from 72.232.194.162: icmp_seq=1 ttl=42 time=252 ms
64 bytes from 72.232.194.162: icmp_seq=2 ttl=46 time=259 ms
--- 72.232.194.162 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2002ms
rtt min/avg/max/mdev = 252.526/256.884/259.202/3.111 ms, pipe 2
Thanks for the help...
8-)
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- Posts: 10642
- Joined: 2005/08/05 15:19:54
- Location: Northern Illinois, USA
Re: DNS Resolution Problem
You just proved that it can.
nslookup returned the correct address, so your computer
did resolve the address from a DNS server.
Now, why did it not resolve for ping?
What is the contents of /etc/resolv.conf?
nslookup returned the correct address, so your computer
did resolve the address from a DNS server.
Now, why did it not resolve for ping?
What is the contents of /etc/resolv.conf?
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- Posts: 4
- Joined: 2007/06/05 09:57:12
- Location: Jakarta, Indonesia
Re: DNS Resolution Problem
Here is the cantent of my resolv.conf and host.conf
[raiden@shiro ~]$ cat /etc/resolv.conf
nameserver 202.169.33.220
nameserver 202.169.33.222
that make me little dizzy to, because this not only happen for ping only but also for yum, and other application that need to perform DNS lookup.
Thanks for the Help :)
[raiden@shiro ~]$ cat /etc/resolv.conf
nameserver 202.169.33.220
nameserver 202.169.33.222
that make me little dizzy to, because this not only happen for ping only but also for yum, and other application that need to perform DNS lookup.
Thanks for the Help :)
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- Posts: 1478
- Joined: 2006/05/29 16:50:11
- Location: San Francisco, CA
Re: DNS Resolution Problem
You should have a "search" or "domain" statement in your /etc/resolv.conf too.
Re: DNS Resolution Problem
Do you have firewall somewhere?
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- Posts: 4
- Joined: 2007/06/05 09:57:12
- Location: Jakarta, Indonesia
Re: DNS Resolution Problem
@michaelnel
I think the "search domain_name" is not the cause, I already try added to resolv.conf, but it still not work.
@foxb
The firewall is not the problem, because other computers can perform query to DNS server on my resolv.conf, and also there are no policies on the firewall that block DNS query from spesific computer/IP.
Thanks All :-D
Maybe if this still not solved then I just fresh install and upgrade to CentOS 5 :idea:
I think the "search domain_name" is not the cause, I already try added to resolv.conf, but it still not work.
@foxb
The firewall is not the problem, because other computers can perform query to DNS server on my resolv.conf, and also there are no policies on the firewall that block DNS query from spesific computer/IP.
Thanks All :-D
Maybe if this still not solved then I just fresh install and upgrade to CentOS 5 :idea:
Re: DNS Resolution Problem
It is really weird problem....
Maybe you can add centos.org in hosts file and try again if it does not work again probably you need to reinstall.
Maybe you can add centos.org in hosts file and try again if it does not work again probably you need to reinstall.
DNS Resolution Problem
[quote]
nikko_bosatsu wrote:
@michaelnel
I think the "search domain_name" is not the cause, I already try added to resolv.conf, but it still not work.
@foxb
The firewall is not the problem, because other computers can perform query to DNS server on my resolv.conf, and also there are no policies on the firewall that block DNS query from spesific computer/IP.
Thanks All :-D
Maybe if this still not solved then I just fresh install and upgrade to CentOS 5 :idea:[/quote]
Try booting with something like Knoppix (or even hook up a Windows PC) and see if you have the same problem.
nikko_bosatsu wrote:
@michaelnel
I think the "search domain_name" is not the cause, I already try added to resolv.conf, but it still not work.
@foxb
The firewall is not the problem, because other computers can perform query to DNS server on my resolv.conf, and also there are no policies on the firewall that block DNS query from spesific computer/IP.
Thanks All :-D
Maybe if this still not solved then I just fresh install and upgrade to CentOS 5 :idea:[/quote]
Try booting with something like Knoppix (or even hook up a Windows PC) and see if you have the same problem.
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- Posts: 1478
- Joined: 2006/05/29 16:50:11
- Location: San Francisco, CA
Re: DNS Resolution Problem
[quote]
nikko_bosatsu wrote:
@michaelnel
I think the "search domain_name" is not the cause, I already try added to resolv.conf, but it still not work.[/quote]
I didn't think it was the cause either, but it's an error to not have it in the file. It won't cause this problem, but it will cause others.
Look at other resolver-related config files like /etc/nsswitch.conf and /etc/host.conf too, and make sure they are set up right. If all that checks out I think at this point I would be using lower level tools like strace and tcpdump or wireshark to see what's going on.
What nags at me about this is that I have seen it before, where nslookup can resolve but apps such as ping and web browsers that use the resolver library cannot, and it came down to some difference in the way nslookup works compared to the others. Unfortunately I am old and senile and can't remember, and although I just spent some time googling for it couldn't find it there either.
That's why I'm thinking strace and wireshark might be informative.
nikko_bosatsu wrote:
@michaelnel
I think the "search domain_name" is not the cause, I already try added to resolv.conf, but it still not work.[/quote]
I didn't think it was the cause either, but it's an error to not have it in the file. It won't cause this problem, but it will cause others.
Look at other resolver-related config files like /etc/nsswitch.conf and /etc/host.conf too, and make sure they are set up right. If all that checks out I think at this point I would be using lower level tools like strace and tcpdump or wireshark to see what's going on.
What nags at me about this is that I have seen it before, where nslookup can resolve but apps such as ping and web browsers that use the resolver library cannot, and it came down to some difference in the way nslookup works compared to the others. Unfortunately I am old and senile and can't remember, and although I just spent some time googling for it couldn't find it there either.
That's why I'm thinking strace and wireshark might be informative.
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- Posts: 1478
- Joined: 2006/05/29 16:50:11
- Location: San Francisco, CA
Re: DNS Resolution Problem
sb3:/usr/bin# ldd nslookup
libdns.so.16 => /usr/lib/libdns.so.16 (0x00b4e000)
libisc.so.7 => /usr/lib/libisc.so.7 (0x00111000)
libcrypto.so.4 => /lib/libcrypto.so.4 (0x00148000)
libnsl.so.1 => /lib/libnsl.so.1 (0x00d79000)
libpthread.so.0 => /lib/tls/libpthread.so.0 (0x00231000)
libc.so.6 => /lib/tls/libc.so.6 (0x00289000)
libgssapi_krb5.so.2 => /usr/lib/libgssapi_krb5.so.2 (0x00c5d000)
libkrb5.so.3 => /usr/lib/libkrb5.so.3 (0x00dad000)
libcom_err.so.2 => /lib/libcom_err.so.2 (0x00243000)
libk5crypto.so.3 => /usr/lib/libk5crypto.so.3 (0x004c5000)
libresolv.so.2 => /lib/libresolv.so.2 (0x00246000)
libdl.so.2 => /lib/libdl.so.2 (0x00259000)
libz.so.1 => /usr/lib/libz.so.1 (0x0025d000)
/lib/ld-linux.so.2 (0x004ef000)
sb3:/usr/bin# ldd /bin/ping
libresolv.so.2 => /lib/libresolv.so.2 (0x00593000)
libc.so.6 => /lib/tls/libc.so.6 (0x00233000)
/lib/ld-linux.so.2 (0x00601000)
Note that they both use libresolv, but nslookup also uses libdns.
Can /usr/bin/host resolve on your machine? It seems to use the same libs as nslookup.
libdns.so.16 => /usr/lib/libdns.so.16 (0x00b4e000)
libisc.so.7 => /usr/lib/libisc.so.7 (0x00111000)
libcrypto.so.4 => /lib/libcrypto.so.4 (0x00148000)
libnsl.so.1 => /lib/libnsl.so.1 (0x00d79000)
libpthread.so.0 => /lib/tls/libpthread.so.0 (0x00231000)
libc.so.6 => /lib/tls/libc.so.6 (0x00289000)
libgssapi_krb5.so.2 => /usr/lib/libgssapi_krb5.so.2 (0x00c5d000)
libkrb5.so.3 => /usr/lib/libkrb5.so.3 (0x00dad000)
libcom_err.so.2 => /lib/libcom_err.so.2 (0x00243000)
libk5crypto.so.3 => /usr/lib/libk5crypto.so.3 (0x004c5000)
libresolv.so.2 => /lib/libresolv.so.2 (0x00246000)
libdl.so.2 => /lib/libdl.so.2 (0x00259000)
libz.so.1 => /usr/lib/libz.so.1 (0x0025d000)
/lib/ld-linux.so.2 (0x004ef000)
sb3:/usr/bin# ldd /bin/ping
libresolv.so.2 => /lib/libresolv.so.2 (0x00593000)
libc.so.6 => /lib/tls/libc.so.6 (0x00233000)
/lib/ld-linux.so.2 (0x00601000)
Note that they both use libresolv, but nslookup also uses libdns.
Can /usr/bin/host resolve on your machine? It seems to use the same libs as nslookup.