you could just run a ping test, such as
from terminal, or
to see if your network card has received a proper ip from DHCP (if you're using DHCP).
shows you the gateway
if you're not using dhcp, you have to set up the config, either via the gui-tool of your
W/DM or terminal
sudo vim /etc/network/interfaces (this is on a debian box, reckon red hat based are similar)