For ssh and ping to local machines with out the .local extension I added them to my /ets/hosts file.

A normal user does not have permission so you have to use sudo. If you os x account has admin privlages it will prompt you for your password. If you have not used vim before, i for insert mode (like a standard text editor), esc to exit insert mode and :wq to write and quit.

sudo vim /etc/hosts

# Host Database
# localhost is used to configure the loopback interface
# when the system is booting.  Do not change this entry.  
##	localhost	broadcasthost
::1             localhost 
fe80::1%lo0	localhost

## Append Local fixed ip Machines   router macmini krypton backup