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My /etc/resolv.conf looks like this:

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 127.0.1.1

# OpenDNS Fallback (configured by Linux Mint in /etc/resolvconf/resolv.conf.d/tail).
nameserver 208.67.222.222
nameserver 208.67.220.220   

When I use nslookup, I seem to use 127.0.1.1:

moose@pc08 ~ $ nslookup www.google.com
Server:     127.0.1.1
Address:    127.0.1.1#53

Non-authoritative answer:
Name:   www.google.com
Address: 173.194.44.17
Name:   www.google.com
Address: 173.194.44.16
Name:   www.google.com
Address: 173.194.44.19
Name:   www.google.com
Address: 173.194.44.18
Name:   www.google.com
Address: 173.194.44.20

But when I right-click on network manager and click on "connection information" I get:

connection information

whois 217.0.43.129 reveals that this belongs to Deutsche Telekom AG, my ISP.

Why does network manager show this information? What DNS server am I currently using?

dnsmasq

Yes, I seem to run dnsmasq:

moose@pc08 ~ $ ps aux | grep dnsmasq
nobody    1479  0.0  0.0   5468  1404 ?        S    14:16   0:00 /usr/sbin/dnsmasq --no-resolv --keep-in-foreground --no-hosts --bind-interfaces --pid-file=/var/run/sendsigs.omit.d/network-manager.dnsmasq.pid --listen-address=127.0.1.1 --conf-file=/var/run/nm-dns-dnsmasq.conf --cache-size=0 --proxy-dnssec --enable-dbus=org.freedesktop.NetworkManager.dnsmasq --conf-dir=/etc/NetworkManager/dnsmasq.d
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2 Answers 2

up vote 10 down vote accepted

You are using dnsmasq, a lightweight forwarding DNS server that runs locally under the control of NetworkManager. Dnsmasq forwards DNS queries to the DNS servers whose addresses have been provided by the DHCP server. It is also possible to set these DNS server addresses statically using the Connection Editor.

The dnsmasq executable is provided by the dnsmasq-base package on which the network-manager package depends. There is also a package called simply "dnsmasq" which also depends on dnsmasq-base, but this "dnsmasq" package should only be installed if you want to run dnsmasq independently of NetworkManager in order to take advantage of features other than mere DNS forwarding.

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@jdthood - your changes are quite extensive and could be construed to go beyond the OP's intent. Please create your own answer if required to support your thoughts. Thanks. –  fossfreedom Mar 26 '13 at 13:54
    
@jdthood: I do appreciate your effort to ensure a correct answer. It is however my understanding that the default behavior of dnsmasq, as integrated with NetworkManager, is to cache 150 entries in accordance with their respective TTL settings. –  Roy Mar 26 '13 at 13:58
    
By default NM-dnsmasq's cache is disabled. Do ps -ef|grep dnsmasq and look for the option --cache-size=0. –  jdthood Mar 26 '13 at 14:17
    
That's not the case on my 12.04 box, but a google search shows that you are right, that is the default on both 12.04 and 12.10. So, a caching DNS server with caching disabled then :) –  Roy Mar 26 '13 at 15:49

You're using the 217.0.43.129. if both your primary and secondary DNS are not found, it'll go to your router and use the DNS server configured in the router. If that DNS fails as well, it'll probabely try to connect to the openDNS server. as configured in /etc/resolv.conf.

https://lists.isc.org/pipermail/bind-users/2006-October/064570.html

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