[CLOSED] weird automatic named request

[warron.french]

Why are my centos machines attempt to resolve hosts that I am not asking it to?

For example, in my /var/log/messages file on my DNS server I see lines with the following:

Feb 26 16:18:59 wsf-LabDNS named[1330]: error (network unreachable) resolving 'mirror.dmacc.net/A/IN': 2001:500:2f::f#53
Feb 26 16:18:59 wsf-LabDNS named[1330]: error (network unreachable) resolving 'mirror.dmacc.net/AAAA/IN': 2001:500:2f::f#53
Feb 26 16:18:59 wsf-LabDNS named[1330]: error (network unreachable) resolving 'reflector.westga.edu/A/IN': 2001:500:2f::f#53
Feb 26 16:18:59 wsf-LabDNS named[1330]: error (network unreachable) resolving 'reflector.westga.edu/AAAA/IN': 2001:500:2f::f#53
Feb 26 16:18:59 wsf-LabDNS named[1330]: error (network unreachable) resolving 'mirrors.tummy.com/A/IN': 2001:500:2f::f#53
Feb 26 16:18:59 wsf-LabDNS named[1330]: error (network unreachable) resolving 'mirrors.tummy.com/AAAA/IN': 2001:500:2f::f#53
Feb 26 16:19:03 wsf-LabDNS named[1330]: client 192.168.2.242#55248: query: mirror.lstn.net IN A + (192.168.2.241)
Feb 26 16:19:03 wsf-LabDNS named[1330]: error (network unreachable) resolving 'mirror.lstn.net/A/IN': 2001:500:1::803f:235#53
Feb 26 16:19:03 wsf-LabDNS named[1330]: client 192.168.2.242#55248: query: mirror.lstn.net IN AAAA + (192.168.2.241)
Feb 26 16:19:04 wsf-LabDNS named[1330]: error (network unreachable) resolving 'mirror.cs.princeton.edu/A/IN': 2001:503:ba3e::2:30#53
Feb 26 16:19:04 wsf-LabDNS named[1330]: error (network unreachable) resolving 'mirror.cs.princeton.edu/AAAA/IN': 2001:503:ba3e::2:30#53
Feb 26 16:19:04 wsf-LabDNS named[1330]: error (network unreachable) resolving 'apple/A/IN': 2001:503:ba3e::2:30#53
Feb 26 16:19:08 wsf-LabDNS named[1330]: client 192.168.2.242#57628: error sending response: host unreachable
Feb 26 16:19:08 wsf-LabDNS named[1330]: error (network unreachable) resolving 'mirror.lstn.net/A/IN': 2001:503:ba3e::2:30#53
Feb 26 16:19:08 wsf-LabDNS named[1330]: error (network unreachable) resolving 'mirror.lstn.net/AAAA/IN': 2001:503:ba3e::2:30#53
Feb 26 16:19:09 wsf-LabDNS named[1330]: error (network unreachable) resolving 'mirror.freedomvoice.com/A/IN': 2001:503:ba3e::2:30#53
Feb 26 16:19:09 wsf-LabDNS named[1330]: error (network unreachable) resolving 'mirror.freedomvoice.com/AAAA/IN': 2001:503:ba3e::2:30#53

Why is trying to resolve:
mirror.dmacc.net,
reflector.westga.edu,
mirrors.tummy.com,
mirror.lstn.net,
mirror.cs.princeton.edu and
mirror.freedomvoice.com

I do not have the standard CentOS repos on my system, because I removed them (I maintain a repo on an isolated network).

Thanks for any suggestions, these automated DNS requests are driving me nuts because they are distracting.
\\War

[WhatsHisName]

They are probably mirrors for repos you have enabled (e.g., adobe, epel, elrepo...) in yum or they are in a mirrorlist= somewhere and yum fastestmirror (or whatever it is called these days) is doing timed access checks.

Try this:

Code: Select all

grep mirrorlist /etc/yum.repos.d/*

or 

grep mirrorlist /etc/yum.repos.d/*|grep -v ':#'

and

grep mirrorlist /etc/yum.conf

[warron.french]

Thanks for the suggestion WhatHisName, but none of those showed me anything.

I moved the original CentOS-*.repo files into a subdirectory of /etc/yum.repos.d would that have any effect?

Thanks,
\\War

[aks]

You're getting IPv6 results back from the DNS lookup, but I guess you don't have IPv6 enabled, so it's an error. Assuming yum still works alright, I think it's okay to ignore those entries (mainly because I visited a couple of the mentioned mirrors and they are just Linux software repositories - if you want to be sure, visit each one in turn).

[warron.french]

Hi aks,
I actually wanted to disable the interfaces IPv6 protocols automatically through the kickstart process which is used to build the workstations.

Howeverm the --noipv6 switch does not actually work. Someone said that I need to manipulate the files to set some VARIABLE to disable IPV6. I still have not done that yet. Do you think that this approach would resolve the issue? I am guessing it would - what about you?

[aks]

I would not disable IPv6. Why disable it? Often that'll break things like postfix. I'd set it to link local or something like that. Anyway, from CentOS FAQ:

5. How do I disable IPv6?

Upstream employee Daniel Walsh recommends not disabling the ipv6 module, as that can cause issues with SELinux and other components, but adding the following to /etc/sysctl.conf:

net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1

To disable in the running system:

echo 1 > /proc/sys/net/ipv6/conf/all/disable_ipv6
echo 1 > /proc/sys/net/ipv6/conf/default/disable_ipv6

or

sysctl -w net.ipv6.conf.all.disable_ipv6=1
sysctl -w net.ipv6.conf.default.disable_ipv6=1

Additional note #1: If problems with X forwarding are encountered on systems with IPv6 disabled, edit /etc/ssh/sshd_config and make either of the following changes:

(1) Change the line

#AddressFamily any

to

AddressFamily inet

(inet is ipv4 only; inet6 is ipv6 only)

or

(2) Remove the hash mark (#) in front of the line

#ListenAddress 0.0.0.0

Then restart ssh.

Additional note #2: If problems with starting postfix are encountered on systems with IPv6 disabled, either

(1) edit /etc/postfix/main.cf and comment out the localhost part of the config and use ipv4 loopback.

#inet_interfaces = localhost
inet_interfaces = 127.0.0.1

or

(2) take out the ipv6 localhost from /etc/hosts .

Additional Note #3 : To disable RPCBIND ipv6 (rpcbind, rpc.mountd, prc.statd) remark out the udp6 and tcp6 lines in /etc/netconfig:

udp tpi_clts v inet udp - -
tcp tpi_cots_ord v inet tcp - -
#udp6 tpi_clts v inet6 udp - -
#tcp6 tpi_cots_ord v inet6 tcp - -
rawip tpi_raw - inet - - -
local tpi_cots_ord - loopback - - -
unix tpi_cots_ord - loopback - - -

[warron.french]

aks, thank you. I will attempt these later today.

I appreciate the assistance,