Named service problem

[Luis Cardenas Perez]

We have an HPUX 10.20 machine as DNS server for a small office (15-20 devices). It's an old server we know, but it had been working for 5 or more years as DNS and legacy applications server. Three days ago, it started to have problems with name resolution without our intervention. I don't know if the root servers' IP's have changed at all, but the message we receive from syslog is this one:
named[477]: ns_req: no address for root server
We downloaded the last db.cache from internic and restarted the service without positive results, it keeps doing the same. Is there a way to solve this.

[Geoff Wild]

It usually means that you use forwarders but the forwarders are not listed or not reachable...

Chack your named.conf file. (or is this running bind 4 - scary stuff!)

Rgds...Geoff

[A. Clay Stephenson]

As mentioned this is usually a problem associated with forwarders. Have there been any firewall changes recently? That may be why you cannot reach any forwarders.

[Luis Cardenas Perez]

We have a forwarder defined, but it's reachable. It's an IP from our ISP. We have a firewall but we haven't changed it's configuration.

[Steven E. Protter · Accepted solution]

Shalom,

Perhaps your ISP changed the address of the DNS servers.

Perhaps your networking department decided that traffic on port 53 was not needed.

Perhaps your ISP is having system problems, give them a call.

Diagnostic:
tcpdump -i lan0 port 53

Take a look at the activity and see whats going on. Post questions.

SEP

[Luis Cardenas Perez]

Thanks all for your responses. I'm going to check the firewall, it could be the problem.

I have tested ISP's dns servers and they seem to be working as usual.
I'm not running bind.
I don't have tcpdump, but I tested with nslookup and I can solve names properly with ISP's dns.

[Geoff Wild]

Do you have dig?

From you HP-UX DNS server:

dig @X.X.X.X hp.com

where X.X.X.X is ip of forwarder.

Or via nslookup

nslookup
> server X.X.X.X
> hp.com

Rgds...Geoff

[Luis Cardenas Perez]

I think it would have been easier having tcpdump, but finally I found the problem, It was Duplex mode in the Server's NIC.
Recently we changed the Switch it was connected to, and the port for that Server was configured Half Duplex.
I changed the Port to Full Duplex and it started to work perfectly again.

Thanks all for your replys.

[Luis Cardenas Perez]

It's finally solved.