Netgear WNR612 Инструкция по эксплуатации онлайн [66/99] 7840

Advanced Settings

N150 2-Port Wireless Router WNR612v3

process information. Before forwarding your message to the remote computer, your router

has to modify the source information and 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:

1. You open a browser and your operating system assigns port number 5678 to this

browser session.

2. You type http://www.example.com into the URL field and your computer creates a web page

request message with the following address and port information. The request message is

sent to your router.

Source address. Your computer’s IP address.

Source port number. 5678, which is the browser session.

Destination address. The IP address of www.example.com, which your computer finds

by asking a DNS server.

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 assigned by the router, such as

33333. This is necessary because two computers could independently use 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 there is an active session for port number 33333. 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.