Setting up network on linux machine can be a little challenging if you want to do static ip address.
First you need to be familiar with networking files and commands in linux.
Briefly ifconfig is the command you will use oftenly.
ifconfig will list network interfaces with their IP, and broadcast, netmask.
To see your gateway use route -n
Where is your dns servers?
Well check /etc/resolv.conf
If you want to use dhcp (which is by default on all Debian based systems) you should not touch any of these.
However what if you need to use static configuration?
Then lets take a look at our interfaces file /etc/network/interfaces
Typical static logical device configuration
# The primary network interface
iface eth1 inet static
# The secondary network interface
iface eth0 inet dhcp
Here eth1 was configured to use a static IP: 18.104.22.168
netmask, network, broadcast and gateway ips are also defined here as well as dns-nameservers.
auto means interface will automatically be up after boot.
as you see eth0 use dhcp configuration.
If you want to just change the gateway i then
ifconfig eth1 down
route add default gw 192.1o.119.254
ifconfig eth1 up
For more info you can check this document: http://www.linuxhomenetworking.com/wiki/index.php/Quick_HOWTO_:_Ch03_:_Linux_Networking#How_to_Change_Your_Default_Gateway