System is not resolving (DNS)

[TD Clark]

I have an L2000 running 11.0. DNS is not resolving (local hosts file okay). Nothing on this system has changed for years. We have 2 other L2000's with the same configuration working fine (i.e. the dns server appears to be okay). Any ideas? Thanks!

[Mark McHugh · Accepted solution]

Todd,

Are you saying that any server names in your local host file resolv, but not those you expect to find in DNS? If there is no problem with your DNS server, your /etc/resolv.conf must be incorrect or missing. Have you recently restored from an ignite image? If so this file needs to be restored manually. Also take a look at your nsswitch.conf and be certain the order is what you expect. (Should be hosts --> DNS --> yp if you use it).

Regards,

Mark McHugh

[Mark Greene_1]

Verify the settings in nsswitch.conf and resolv.conf, /etc/netconfig (if present). Make sure that NIS hasn't been enabled. Make sure you can ping your dns server; depending on your network type and setup, this particular box may have been isolated from the dns box.

HTH
mark

[TD Clark]

resolv.conf and nsswitch.conf are there and haven't been changed for over a year. I also looked at the files - they look okay too.

[Olivier ROBERT]

Hi Todd,

Are the L2000s all on the same subnet?
Are the DNS servers the same on all?
Can you ping the DNS servers from the faulty system?
Can you access remotely to the faulty system?
Does your "hosts" resolving policy contain the "dns" source (in /etc/nsswitch.conf)?
Are your resolver configuration files OK? (/etc/hosts, /etc/resolv.conf, /etc/nsswitch.conf)
Do the files contain more/less lines that is seems to contain at a first sight? (Maybe what seems to be a linewrap in your editor is a real newline, compare a "wc -l " with what you see eventually)
Do you use some other source (nis, nisplus)?
Do the files have a suspiciously recent modification time?

Well, that's all I can think of, for now...
Hope this helps,

Olivier

[TD Clark]

I can ping the dns server. The DNS server is the same for all of our systems (this system is the only one that can't resolve) and all of our resolve related files (nsswitch.conf, resolv.conf, netconfig) have not been modified for over a year and look okay.

[Mark Greene_1]

Todd,

Try this: run nslookup without any options. At the > prompt, do "set debug" (without the quotes), and then "set swtrace", and then enter the name of your dns server, and then the ip address of your dns server and see if that sheds any light on this.

mark

[Wilfred Chau_1]

Does the following return anything?

# nslookup

[Geoff Wild]

Actually, just do a:

nslookup

by itself - it will tell you the default server - if you get an error (like server not responding) then you have an issue (maybe dns isn't running on the dns server, or the port has been blocked...etc).

Rgds...Geoff

[harry d brown jr]

What version of Bind are you running?

what /usr/sbin/named

Can you post these files?

/etc/resolv.conf
/etc/nsswitch.conf
/etc/rc.config.d/namesvrs

If you run "named", is it running now and can you post the conf files?

and the output from

netstat -rn
domainname
hostname


live free or die
harry

[Oleg Zieaev_1]

Hi.
I think you may consider checking from nslookup if it is pointing to the proper DNS server. Also make sure you do not run named on you system if you are not dns server.
from nslookup just enter 'policy' to query defined policy reflected in /etc/nsswitch.conf.
From resolv.conf you can specify domain and up to 3 dns servers.
If there is a particular name you can no resolve, it might have corrupted values in dns server like missing . at the /etc/named.data files on your dns server. If only one server has difficulties to resolve names, check ports and network connections along with firewalls settings. Usually /etc/resolv.conf is straight forward file, nothing fancy there.

Hope this helps,
0leg

[Wodisch]

Hi,

did somebody place a firewall between the station and your DNS server(s), or change the firewall rules?
DNS queries use UDP port 53, and firewall admins don't really like UDP, so they usually block it...

FWIW,
Wodisch

[Olivier ROBERT]

Maybe that could be juicy in terms of information contents if you send us a "traceroute " output on both the faulty server and another non-faulty and similarly configured one.

Regards,

Olivier

[Andrew Imm]

To get our HP-UX server to recognize the NT DNS server we went into the /etc/nsswitch.conf & added the following lines;

hosts: files [NOTFOUND=continue] dns

[John Poff]

Hi,

Your resolv.conf and nsswitch.conf files may not have changed, but someone may have changed the permissions on them. I ran into a similar problem once and finally figured out that someone had removed the world readable permission from nsswitch.conf file. Is DNS broken for everybody including root, or just for non-root users?

JP