Linux Testing your network connection

1) First try pining your own IP address to see if your IP address is set properly, syntax is:
ping IP-ADDRESS

If your IP address is 202.54.1.10 then try:
# ping 202.54.1.10

Tip use ifconfig command to see IP address for eth0 or any other interface.

2) Try pinging neighboring machines IP addresses:
# ping 192.168.1.2
# ping 202.54.1.12

If you need to setup/configure network or connecting to the network under Linux use following tools:
Under Red Hat use neat OR system-config-network (Fedora core) command
Uder Debian Linux use network-admin command.

You can also start above command from GUI. Using above GUI tools you should able to configure DNS, hosts, IP address etc. For more information see:
List of LINUX troubleshooting commands/tools part # 1

Halt or stop linux firewall

A firewall is designed to help protect your computer from attack by malicious users or by malicious software (viruses that use unsolicited incoming network traffic to attack).

Also before you disable your firewall, you must disconnect your computer from all networks, including the Internet to avoid damage :D

You would like to Halt linux firewall or stop linux firewall (i.e. flush iptables rules). First login as root user.

Option A – If you are redhat Linux user type command:

If you are using Red Hat (RHEL) / CentOS / Fedora Core Linux, use the following command:

OR

Option B – If you are Debian Linux user type following commands one by one