IP addresses are unique numbers that identify devices on a network. Public IP addresses are used for internet access while private IP addresses are used within local networks. A broadband router shares a public IP connection by assigning private IP addresses to connected devices and providing firewall protection. IP addresses allow communication within the same local network but devices must have the correct IP address range to connect. Network troubleshooting tools like ping help verify connectivity issues.

1. Basic Networking Concepts
1. What is IP address?
IP address is short for Internet Protocol Address. An IP Address is a unique
number that devices use in order to identify and communicate with each other on
a computer network. If two computers have the same IP addresses, it will cause
conflict and cause problem.
IP Addresses are written as a sequence of four numbers separated by ".", like
this: 208.123.246.35.
2. What is Public IP address? What is Private IP address?
Public IP addresses are IP addresses used on Internet. They are internet routeable and are visible to the public. Most people who use Cable/DSL service at
home/office obtain one dynamic Public IP address from ISP (Internet Service
Provider).
Computers on a Local Area Network use Private IP addresses. 192.168.x.x is an
example of a Private IP address.
3. What is the purpose of a broadband router?
The purpose of a broadband router is to share an internet connection among
several computers. The broadband router will get one public IP from your ISP
and assign dynamic private IP address to each of your computer. All of your
computers will have unique private IP address but will use the same public IP
address to browse Internet. The router provides a basic Firewall which can deny
access to your local computers from Internet.
4. Why the IP address of my computers matters?
Usually computers in the same network use the same first three numbers of their
IP address, only the 4th number is different. For example, your router could have
IP address 192.168.2.1 while ethernet desktop uses 192.168.2.100 and wireless
iPad use 192.168.2.102...etc.
If your network uses 192.168.2.x but one computer somehow uses an IP address
of 192.168.1.100, then this computer is not in the same IP network and can not
communicate with 192.168.2.x network.
5. How to find out my computer's private IP address?
If you have Windows 7/Windows Vista computer, click on Start -> go to "Search
Programs and fields" field, enter "cmd" hit Enter key.
If you have Windows XP computer, click on Start -> Run -> type "cmd" or
"command" hit OK.
Under the command prompt, type in "ipconfig" hit Enter. You will see your
computer's IP address (IPv4 address), subnet mask, and default gateway.
Usually the default gateway address is the IP address of your router.
6. How to make my computer obtain a dynamic IP address automatically?

2. Usually we let computers obtain IP address automatically from the router. You
can click on Start -> Run -> type "ncpa.cpl" hit OK. In the Network Connection
window, right click on "Local Area Connection" and select Properties. Double
click on Internet Protocol TCP/IP. Select the option "obtain IP address
automatically" and select the option "obtain DNS server address automatically"
Click OK. Click OK again.
7. What if I prefer to set a static IP rather than dynamic IP address?
If you prefer not to obtain an IP address automatically, you can set static IP
address to your computer. Locate your network connection icon in the Network
Connection window. Go to the property of the network connection. Go to the
Internet Protocol v4 (TCP/IP) Properties. Select the option "use the following IP
address". Manually type in your static IP, subnet mask and default gateway. You
will also need to manually type in the Primary DNS server address. Click OK
twice.
8. What basic tool can I use to trouble shoot my networking problem?
The most popular tool is to use the "PING" command under the command
prompt.
Click on Start -> Run -> type "command" hit OK. Under the command prompt,
type in "ping x.x.x.x" hit Enter The x.x.x.x can be the IP address of your
gateway. For example, type "ping 192.168.2.1" hit Enter. If you receive 4
replies, it means your computer can see that device and get replies.
You also can ping a device on the Internet. For example, "ping 209.191.93.52" is
to ping a Yahoo site on Internet. If you can "ping 209.191.93.52" to get 4 replies
from 209.191.93.52, you do have a good internet connection.
Ping a DNS name on Internet. If you can do "ping www.yahoo.com" and get 4
replies, your computer should able to browse Internet fine. If you can "ping
209.191.93.52" to get 4 replies from 209.191.93.52, but when you "ping
www.yahoo.com" you get "unknown host", you have an Internet connection but
you have a DNS problem to browse Internet. Check your DNS server address by
typing "ipconfig /all" under the command prompt and it will give you some clue.