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syslog: gethostbyaddr: fqdn != x.x.x.x

John Kittel
Trusted Contributor

syslog: gethostbyaddr: fqdn != x.x.x.x

HP-UX 11.11

I get a fair number of messages like this in syslog.log:

Mar 14 13:07:34 syslog: gethostbyaddr: host.mydomain.com. != x.x.x.x

where host is any of several different hosts in our intranet and x.x.x.x is that host's ip number. From the command line I can do nslookup on the name, or the number, and both return the same valid information as what is in the syslog message.

Is this message in syslog.log indicating there is a problem somewhere? or is it just "informational"? I haven't been able to figure out what activity results in these messages.

Ivan Krastev
Honored Contributor

Re: syslog: gethostbyaddr: fqdn != x.x.x.x

Possible errors in one of your DNS servers. See this previous thread -

[Broken link removed on 03-23-2017 by Admin]


John Kittel
Trusted Contributor

Re: syslog: gethostbyaddr: fqdn != x.x.x.x

Thank you. I found that before. It wasn't too much help. No solution or cause was ever specified in that thread. And the question / problem was a little different. In the other case, I think the syslog message said gethostbyaddr returned the wrong address, and the author of the thread confirmed that it was the wrong address.

In my case, I think syslog message is saying gethostbyaddr returned the wrong address, but in fact the address in the message is the correct address for the host.
John Kittel
Trusted Contributor

Re: syslog: gethostbyaddr: fqdn != x.x.x.x

The problem is that when PCs reboot, due to DHCP, Acitve Directory, and DNS, they sometimes look as though they have 2 different ip numbers simultaneously, for short intervals. When I first was investigating this, I did not catch any in the act because I wasn't checking quickly and frequently enough.
Honored Contributor

Re: syslog: gethostbyaddr: fqdn != x.x.x.x

Do you have patch PHNE_29445 applied?
Steven E. Protter
Exalted Contributor

Re: syslog: gethostbyaddr: fqdn != x.x.x.x


DNS lookups are failing.

Possible causes:

1) Microsoft DNS servers.
2) problems with /etc/resolv.conf
3) Problem with how the application is forming its request (bad c code and such).
4) Routers and firewalls attempting to block port 53 udp or tcp.

Steven E Protter
Owner of ISN Corporation
Sponsor: http://hpux.ws
Twitter: http://twitter.com/hpuxlinux
Founder http://newdatacloud.com
John Kittel
Trusted Contributor

Re: syslog: gethostbyaddr: fqdn != x.x.x.x

Yes PHNE_29445 is applied.

Yes, cause is Windows DHCP, Windows Active Directory, Windows DNS servers, and/or our configuration of such. I am not Windows administrator. Once I discovered that DNS lookup of 2 different ip numbers returned same hostname, Windows admin admitted yes, this is a known problem...

I suppose I should have been more explicit in my previous post that I understood the problem (well enough to get it out of my court into theirs) and/or closed the thread.

Thanks for the help.
Frequent Visitor

Re: syslog: gethostbyaddr: fqdn != x.x.x.x

Hai to All,


I have also got same errors in syslog with os version HP unix 11.23.


then i found there was duplicate entries are there at that time reverse name resolution(ip to name).


I have corrected in my dns server resolved my issue.


Thanks to all.


Mahesh Dadi