Possible DNS Problem

[tmurraylf]

Hi,

If I attempt to resolve an unknown domain via ping I receive a ping reply from a host of the domain which the server is a part of. For example say I ping www.notvaliddomain.com I receive a response from server.mydomain.com where mydomain is the domain name which the server is a member of. The problem is machine specific as when I ping the same invalid domain on another machine ping returns unknown host www.notvaliddomain.com.

Anyone have any ideas why this is happening?

Thanks,

Tamkio

[Dolda2000]

That's interesting... if you have the bind-tools installed, run `host www.notvaliddomain.com' on the affected machine and post what that returns. That will help filter out if it's a DNS problem or other name switch misconfiguration.

[tmurraylf]

That's interesting... if you have the bind-tools installed, run `host www.notvaliddomain.com' on the affected machine and post what that returns. That will help filter out if it's a DNS problem or other name switch misconfiguration.

Dolda2000,

Thanks for your reply. I ran host www.notvaliddomain.com and it returned:

Host www.notvaliddomain.com not found: 3(NXDOMAIN)

[Dolda2000]

Then it must be some other weird kind of problem... Can you post your /etc/hosts and /etc/nsswitch.conf?

[tmurraylf]

Then it must be some other weird kind of problem... Can you post your /etc/hosts and /etc/nsswitch.conf?

Here are the files:
hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1 localhost localhost.localdomain


nsswitch.conf
#
# /etc/nsswitch.conf
#
# An example Name Service Switch config file. This file should be
# sorted with the most-used services at the beginning.
#
# The entry '[NOTFOUND=return]' means that the search for an
# entry should stop if the search in the previous entry turned
# up nothing. Note that if the search failed due to some other reason
# (like no NIS server responding) then the search continues with the
# next entry.
#
# Legal entries are:
#
# nisplus or nis+ Use NIS+ (NIS version 3)
# nis or yp Use NIS (NIS version 2), also called YP
# dns Use DNS (Domain Name Service)
# files Use the local files
# db Use the local database (.db) files
# compat Use NIS on compat mode
# hesiod Use Hesiod for user lookups
# [NOTFOUND=return] Stop searching if not found so far
#

# To use db, put the "db" in front of "files" for entries you want to be
# looked up first in the databases
#
# Example:
#passwd: db files nisplus nis
#shadow: db files nisplus nis
#group: db files nisplus nis

passwd: files
shadow: files
group: files

#hosts: db files nisplus nis dns
hosts: files dns

# Example - obey only what nisplus tells us...
#services: nisplus [NOTFOUND=return] files
#networks: nisplus [NOTFOUND=return] files
#protocols: nisplus [NOTFOUND=return] files
#rpc: nisplus [NOTFOUND=return] files
#ethers: nisplus [NOTFOUND=return] files
#netmasks: nisplus [NOTFOUND=return] files

bootparams: nisplus [NOTFOUND=return] files

ethers: files
netmasks: files
networks: files
protocols: files
rpc: files
services: files

netgroup: files

publickey: nisplus

automount: files
aliases: files nisplus

Thanks again.

[Dolda2000]

Nothing wrong there either. Do other programs that use the nsswitch calls exhibit the same behavior (like `traceroute www.notvaliddomain.com')?

[tmurraylf]

Nothing wrong there either. Do other programs that use the nsswitch calls exhibit the same behavior (like `traceroute www.notvaliddomain.com')?

Yes, same behavior. This is hard to solve. I first noticed the problem when I pointed my web browser at a site that was unreachable and our web site default page was displayed.

[Dolda2000]

Of course, the great thing with Linux is that issues like this always can be solved. The more sophisticated debugging methods are very hard to use without access to the actual computer, though. I still have some tricks left up my sleeves, though. Can you run the following command, which will generate a file called `ping.strace', and mail that file to me (I'll put it up on my HTTP server so that everyone can see it)?

strace -o ping.strace -f ping www.notvaliddomain.com

[tmurraylf]

Dolda2000,

Just getting back to this project...I finally solved the mistery. I changed the hostname on the test server from the fully qualified name e.g. server.mydomain.com to just the hostname of server. Now when I ping notavaliddomain ping returns: unknown host notvaliddomain.com

Thanks again for all you help.