identifying failures to resolve names to addresses on Redhat Linux.

We're having a problem with resolving a name to an address with a Linux apps.  We have an activity where we're moving images from one company network to another.  We have been trying to ensure all references to domain names have been changed, but we're still getting an error and so we're thinking we've missed one (or more).  Is there something that can trap attempts to resolve a name to an address we can turn on or check (either on our server or the network)?  I'm not even sure if a sniffer might help, but we're looking for any ideas that people may have.
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Gene KlamerusTechnical ArchitectAsked:
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Gene KlamerusTechnical ArchitectAuthor Commented:
to clarify, we don't know the server name that can't be resolved.  That's what we want to capture so we have some idea of what to look for in application configuration to change.
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nociSoftware EngineerCommented:
Well the program doing the moving needs to resolve the name, and should complain when it can't.
There is no "official" method to trap failures.

What you could do is scan the network packets for port 53 udp (DNS queries)  and all responses that have failures filtered out using f.e. wireshark.
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Gene KlamerusTechnical ArchitectAuthor Commented:
There is no program moving anything.  People moved the server.

Does Wireshark exist for Linux?
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Gene KlamerusTechnical ArchitectAuthor Commented:
sorry, I checked on Linux myself.  That's a possibility.
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nociSoftware EngineerCommented:
Wieshark was born on Solaris & Unix as Ethereal, and later ported to windows.. Even before NT existed. So yes it is available.
t-shark should be sufficent though.
With images my first idea is Pictures...   VM Images are different.

Ok then is the DNS still available (see /etc/resolv.conf )  if on localhsot can the DNS server still reach the outside world?
If IP address in the environment changes were the NAT rules adjusted?
iptables -t nat -L -nv --line
iptables -t filter -N -nv --line

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Gene KlamerusTechnical ArchitectAuthor Commented:
We may need to do this, however we've also been making other changes with input from Oracle (this is for an Oracle product) that may be negating the need or resolving an issue elsewhere that is causing this problem.  TBD.
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nociSoftware EngineerCommented:
ok np. good luck solving the moving issues.
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Gerwin Jansen, EE MVETopic Advisor Commented:
Already closed, but from within Linux you can run tcpdump (as root) for a while and store the captured data in a file.

Then use Wireshark to load the capture file and look for DNS requests that fail, or possible other issues like connects that fail to non-existing ip addresses.
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