1. The Debian Avahi (nss-mdns) Bug
There is a known bug doing the rounds in Debian based distros, this includes Ubuntu.
The problem is in the nsswitch.conf file where wins mdns causes a slowdown of DNS resolution on some machines.
A simple workaround for this problem is to remove mdns4_minimal entry from the nsswitch.conf file, or change mdns4_minimal to just mdns4 (whichever works best for you):
Edit this file- /etc/nsswitch.conf
Scroll down to the entry which says:
hosts: files dns wins mdns4_minimal
and delete the mdns4_minimal entry. (I removed wins as well), s it looks like this:
hosts: files dns
2. Check your DNS in resolv.conf
You should only have two entries (usually) which are your Internet Service Provider’s DNS servers.
Check and/or edit your dns servers:
gksudo scite /etc/resolv.conf
It should look something like this:
You may have an extra IP address there, possibly your router (192.168.1.1), and if you haven’t got dns servers configured in your router config, this may cause a problem/slowdown as well. EG:
Just remove the first one and leave the two ISP DNS server IP’s.
original link http://ubuntuforums.org/showthread.php?t=1487039&page=2