You can remove that warning by adding 

export ROS_IP=127.0.0.1

to ~/ros/setup.sh but the warning is harmless as far as I know since
127.0.1.1 and 127.0.0.1 are both localhost.

On Thu, 2010-05-27 at 17:57 +0530, Narasimhan Rajagopal wrote: 
> as per tutorials when i started roscore i get the following warning.
> is it ok.

> WARNING: IP address 127.0.1.1 for local hostname 'narasimhan-desktop'
> does not appear to match
> any local IP address (127.0.0.1). Your ROS nodes may fail to
> communicate.