cannot ping [/my_turtle]: unknown node [closed]

edit

working the tutorials, all went well until

[code] rosnode ping my_turtle [/code]

got back

[code] rosnode: node is [/my_turtle] cannot ping [/my_turtle]: unknown node [/code]

Verified path, network setup, etc all went exactly as described until ping. First time working with ROS, what should I look at next?

edit: went back through tutorial, but before changing name of turtlesim to my_turtle, pinged turtlesim and it worked fine.

regards, Richard