NSLOOKUP and DNS queries not working with my CentOS 5 installation?

Hi Folks

I'm stumped. I've just installed a new CentOS server and cannot get the DNS to resolve anything, no matter what I put in the resolve.conf file. It will ping OK if I enter an IP address but if I try to ping something that needs a resolve, NADA!

IPTables and SELinux is OFF. The main firewall that protects all our servers is set to ALLOW ALL from internal network to outside.

If I do an nslookup destination dns_serverIP it works fine but simply will not resolve a name to an IP.

Can anyone help? I need to get this server live ASAP and this is holding me up.

Cheers
Chris
kenwardcAsked:
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omarfaridConnect With a Mentor Commented:
A connection time out, means that you are not able to reach to the server or the server is down:

- Check again the firewalls (port 53 udp/tcp both ways) in the way to the dns server
- Check the routing and reachability to the server
- Check if the server ip is correct
- If you own the dns server, then check if the dns server process is not misbehaving
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TintinCommented:
Do you have an internal DNS server or are you relying on an external DNS server?

What entry/s did you try in /etc/resolv.conf?

In /etc/nsswitch.conf, do you have:

hosts:      files dns

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kenwardcAuthor Commented:
Hi there, Tintin

Yes - I'm using external DNS servers - both ours and both working fine with all our other servers.
I've changed the entries in resolv.conf to other DNS servers with the same results.

nsswitch.conf has the:
hosts   files  dns
entry in it.

Cheers
Chris
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TintinCommented:
What is the output of

host -v google.com
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kenwardcAuthor Commented:
Hi Tintin

"Connection timed out. No servers could be reached"

I believe the servers are DNS servers and of course it all points to firewall issue but the firewall is set to allow ALL and the CentOS firewall is definitely off. <scratch>

Cheers
Chris
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joolsCommented:
post your resolv.conf
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kenwardcAuthor Commented:
Hi jools

I don't want to publicly post the details for our DNS servers. The resolv.conf file simply contains two lines. On each line there is a DNS server listed. That's it. The same resolv.conf file is in use on 4 other CentOS servers and all working fine.

Cheers
Chris
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joolsCommented:
it is called resolv.conf and not resolve.conf as you posted earlier then?
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joolsCommented:
also, the resolv.conf should read;

nameserver <ipaddress>
nameserver <ipaddress>

is that what you meant when you said `On each line there is a DNS server listed. That's it.`
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kenwardcAuthor Commented:
Hi Jools
Yes - sorry - it's exactly that - resolv.conf and the entries are as you mention.

Cheers
Chris
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TintinCommented:
When you say

"If I do an nslookup destination dns_serverIP it works fine"

Do you mean that when you are on the CentOS server, you do

nslookup 123.123.123.123 1.2.3.4

the IP address resolves correctly to the name, but not the other round?

Also, when you say:

"It will ping OK if I enter an IP address"

Is "it" one of the DNS servers?

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