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•
Destination port number. 80, which is the standard port number for a web server
process.
3.
Your router creates an entry in its internal session table describing this communication
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):
•
The source address is replaced with your router's public IP address. This is
necessary because your computer uses a private IP address that is not globally
unique and cannot be used on the Internet.
•
The source port number is changed to a number chosen by the router, such as 33333.
This is necessary because two computers could independently be using the same
session number.
Your router then sends this request message through the Internet to the web server at
www.example.com.
4.
The web server at www.example.com composes a return message with the requested web
page data.
The return message contains the following address and port information. The web server
then sends this reply message to your router.
•
Source address. The IP address of www.example.com.
•
Source port number. 80, which is the standard port number for a web server
process.
•
Destination address. The public IP address of your router.
•
Destination port number. 33333.
5.
Upon receiving the incoming message, your router checks its session table to determine
whether an active session for port number 33333 exists.
Finding an active session, the router then modifies the message to restore the original
address information replaced by NAT. Your router sends this reply message to your
computer, which displays the web page from www.example.com. The message now
contains the following address and port information.
Source address. The IP address of www.example.com.
Source port number. 80, which is the standard port number for a web server process.
Destination address. Your computer's IP address.
Destination port number. 5678, which is the browser session that made the initial
request.
6.
When you finish your browser session, your router eventually detects a period of inactivity in
the communications.
Your router then removes the session information from its session table, and incoming
traffic is no longer accepted on port number 33333.
N600 Wireless Dual Band Router JNDR3000
Advanced Settings
100
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