Allowing Inbound Connections To Your Network; How Your Computer Accesses A Remote Computer Through Your Router57 - NETGEAR WNR612v2 User Manual

Wireless-N 150 Router WNR612v2 User Manual

Allowing Inbound Connections to Your Network

By default, the wireless router blocks any inbound traffic from the Internet to your computers
except for replies to your outbound traffic. However, you might need to create exceptions to
this rule for the following purposes:
To allow remote computers on the Internet to access a server on your local network.
•
To allow certain applications and games to work correctly when their replies are not
•
recognized by your router.
Your router provides two features for creating these exceptions: port forwarding and port
triggering. This section explains how a normal outbound connection works, followed by two
examples explaining how port forwarding and port triggering operate and how they differ.
How Your Computer Accesses a Remote Computer through
Your Router
When a computer on your network needs to access a computer on the Internet, your
computer sends your router a message containing source and destination address and
process information. Before forwarding your message to the remote computer, your router
must modify the source information and must create and track the communication session so
that replies can be routed back to your computer.
Here is an example of normal outbound traffic and the resulting inbound responses:
You open Internet Explorer, beginning a browser session on your computer. Invisible to
1.
you, your operating system assigns a service number (port number) to every
communication process running on your computer. In this example, let's say Windows
assigns port number 5678 to this browser session.
You ask your browser to get a Web page from the Web server at www.example.com. Your
2.
computer composes a Web page request message with the following address and
port information:
The source address is your computer's IP address.
•
The source port number is 5678, the browser session.
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The destination address is the IP address of www.example.com, which your computer
•
finds by asking a DNS server.
The destination port number is 80, the standard port number for a Web server
•
process.
Your computer then sends this request message to your router.
Your router creates an entry in its internal session table describing this communication
3.
session between your computer and the Web server at www.example.com. Before sending
the Web page request message to www.example.com, your router stores the original
information and then modifies the source information in the request message, performing
Network Address Translation (NAT):
Chapter 6: Fine-Tuning Your Network | 57