I can browse sites using firefox configured with proxy

172.1.6.0.6:3128  
resolv.conf  
domain   pudhcp.ac.in  
search pudhcp.ac.in  
nameserver 172.16.0.7

I checked with Windows and I found the same DNS server settings

127.0.0.1       bt  
127.0.1.1       bt  

Above is the hosts file

I modified the top line from localhost to bt still not working bt is the hostname
Still I can't ping to google.com - it is showing

unable to resolv hostname

I tried all solutions,I guess proxy is used even for DNS resolution

root@bt:~# dhclient  
There is already a pid file /var/run/dhclient.pid with pid 7157  
killed old client process, removed PID file  
Internet Systems Consortium DHCP Client V3.1.1  
Copyright 2004-2008 Internet Systems Consortium.  
All rights reserved.  
For info, please visit http://www.isc.org/sw/dhcp/  

Listening on LPF/eth1/5c:ac:4c:b1:0c:7c  
Sending on   LPF/eth1/5c:ac:4c:b1:0c:7c  
Listening on LPF/eth0/60:eb:69:18:4d:3d  
Sending on   LPF/eth0/60:eb:69:18:4d:3d  
Sending on   Socket/fallback  
DHCPREQUEST of 172.16.6.87 on eth0 to 255.255.255.255 port 67  
DHCPACK of 172.16.6.87 from 172.16.6.1  
bound to 172.16.6.87 -- renewal in 79432 seconds.