Convert DHCP configuration to static IP configuration

based on this source (for Ubuntu) 
Desired new sample settings:
= Host IP address 200.87.229.20
= Netmask: 255.255.255.252
= Network ID: 200.87.229.0
= Broadcast IP: 200.87.229.255
= Gateway/Router IP: 200.87.229.17
= DNS Server: 8.8.8.8

Open network configuration file:

sudo nano /etc/network/interfaces

Find and remove dhcp entry:
iface eth0 inet dhcp
Append new network settings:
iface eth0 inet static
address 200.87.229.20
netmask 255.255.255.252
network 200.87.229.0
broadcast 200.87.229.255
gateway 200.87.229.17
Save and close the file. Restart the network:
$ sudo /etc/init.d/networking restart
Task: Define new DNS servers Open /etc/resolv.conf file
$ sudo nano /etc/resolv.conf
You need to remove old DNS server assigned by DHCP server:
search myisp.com
nameserver 200.87.229.254
nameserver 8.8.8.8
Save and close the file.
Task: Test DNS server 
 $ host cyberciti.biz
Network command line cheat sheet You can also use commands to change settings. Please note that these settings are temporary and not the permanent. Use above method to make network changes permanent or GUI tool as described below.
Task:
Display network interface information 
$ ifconfig
Task: 
Take down network interface eth0
/ take a network interface down 
$ sudo ifconfig eth0 down
OR
$ sudo ifdown eth0
Task: 
Bring a network interface eth0 up  
$ sudo ifconfig eth0 up
OR 
$ sudo ifup eth0
Task: Change IP address and netmask from command lineActivate network interface eth0 with a new IP (192.168.1.50) / netmask:
$ sudo ifconfig eth0 192.168.1.50 netmask 255.255.255.0 up
Task: Display the routing table  
$ /sbin/route
OR
$ /sbin/route -n
Output:

Kernel IP routing table 

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
localnet        *               255.255.255.0   U     0      0        0 ra0 

200.87.229.0    *               255.255.255.0   U     0      0        0 eth0 

172.16.236.0    *               255.255.255.0   U     0      0        0 eth1
default        200.87.229.254   0.0.0.0         UG    0      0        0 ra0 

Task: Add a new gateway  
$ sudo route add default gw 172.16.236.0
Task: Display current active Internet connections
(servers and established connection) 
$ netstat -nat
Task: Display open ports
 $ sudo netstat -tulp
OR 
$ sudo netstat -tulpn
Task: Display network interfaces stats (RX/TX etc) 
$ netstat -i
Task: Display output for active/established connections only
$ netstat -e
$ netstat -te
$ netstat -tue

Where

• -t : TCP connections
• -u : UDP connections
• -e : Established

Task: Test network connectivity
Send ICMP ECHO_REQUEST to network hosts, routers, servers etc with ping command. This verifies connectivity exists between local host and remote network system:
$ ping router
$ ping 192.168.1.254
$ ping cyberciti.biz
See simple Linux system monitoring with ping command and scripts for more information.
Task: Use GUI (Graphical Configuration) network Tool If you are new, use GUI configuration tool, type the following command at terminal:
$ network-admin &
Above command is Ubuntu's GUI for configuring network connections tool.
Final tip - Learn how find out more information about commandsA man page is your best friend when you wanted to learn more about particular command or syntax. For example, read detailed information about ifconfig and netstat command:
$ man ifconfig
$ man netstat
Just get a short help with all command options by appending --help option to each command:
$ netstat --help
Find out what command is used for particular task by searching the short descriptions and manual page names for the keyword:
$ man -k 'delete directory'
$ apropos -s 1 remove
Display short descriptions of a command:
$ whatis rm
$ whatis netstat