Netgear N 900 Manual

							Advanced Settings91
 N900 Wireless Dual Band Gigabit Router WNDR4500
2.
Select  Advanced > Advanced Setup > Wireless Repeating Function  to display the 
Wireless Repeating Function screen.
Scroll to view 
more settings
3. In the Wireless Repeating Function screen (depending on the frequency you want to use), 
select the  Enable Wireless Repeating Function check box and select the  Wireless Base 
Station  radio button.
4. Ente r the MAC address for one or more repeater units.
5. Click  Appl
 y to save your changes.
Set Up a Repeater Unit
Use a wired Ethernet connection to set up the repeater unit to avoid conflicts with the 
wireless connection to the base station.
Note:If you are using the WNDR4500 base station with a non-NETGEAR 
router as the repeater, you might need to change additional 
configuration settings. In particul ar, you should disable the DHCP 
server function on the wireless repeater AP.
To configure the router as a repeater unit:
1. Log in to the router that will be the repeater. Select  Basic > W
 ireless Settings and 
verify that the wireless settings match the bas e unit exactly. The wireless security option 
has to be set to  WEP or None .
2. Select  Adv
 anced > Wireless Repeating Function , and select the Enable Wireless 
Repeating Function check box  and the Wireless Repeater radio button.
3. Fill in  the Repeater IP Address field. This IP  address 
 has to be in the same subnet as the 
base station, but different from the LAN IP address of the base station. 
						

							Advanced Settings92
N900 Wireless Dual Band Gigabit Router WNDR4500 
4.
Click  Apply  to save your changes.
5. V
erify connectivity across the LANs. 
A computer on any wireless or wired LAN segment of the router should be able to 
con
nect to the Internet or share files and printers with any other wireless or wired 
computer or server connected to the other access point.
Port Forwarding and Triggering
By default, the router blocks inbound traffic from t he Internet to your computers except replies 
to your outbound traffic. You might need to create exceptions to this rule for these purposes:
• T
o allow remote computers on the Internet to access a server on your local network. 
•T
o allow certain applications and games to work correctly when their replies are not 
recognized by your router.
Your router provides two features for creat in
 g these exceptions: port forwarding and port 
triggering. The next sections provide background information to help you understand how 
port forwarding and port triggering work, and the differences between the two.
Remote Computer Access Basics
When a computer on your network needs to access a computer on the Internet, your 
computer sends your router a message containing the source and destination address and 
process information. Before forwarding your  message to the remote computer, your router 
has to modify the source information and crea te 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. Y
ou open a browser, and your operating system assigns port number 5678 to this 
browser session. 
2. Y
ou 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 . Y
 our computer’s IP address.
Source port number . 567
 8, which is the browser session. 
Destination address . The I
 P address of www.example.com, which your computer finds 
by asking a DNS server.
Destination port number . 80, which is th
 e standard port number for a web server 
process.
3. Y
our 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  
						

							Advanced Settings93
 N900 Wireless Dual Band Gigabit Router WNDR4500
information and then modifies the source information in the request message, performing 
Network Address Translation (NAT):
•
T
he 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.
• T
he 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 th rough
  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 a
 ddress of www.example.com.
Source port number . 80, which is the
  standard port number for a web server process.
Destination address. T
 he public IP address of your router.
Destination port number . 3
 3333.
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.
Source address . The IP a
 ddress of www.example.com.
Source port number . 80, which is the
  standard port number for a web server process.
Destination address. Y
 our computer’s IP address.
Destination port number . 5
 678, 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.
Port Triggering to Open Incoming Ports
In the preceding example, requests are sent to  a remote computer by your router from a 
particular service port number, and replies from  the remote computer to your router are 
directed to that port number. If the remote server sends a reply back to a different port 
number, your router does not recognize it and discards it. However, some application servers 
(such as FTP and IRC servers) send replies back to multiple port numbers. Using the port 
triggering function of your router, you can tell the router to open additional incoming ports 
when a particular outgoing port originates a session. 
						

							Advanced Settings94
N900 Wireless Dual Band Gigabit Router WNDR4500 
An example is Internet Relay Chat (IRC). Yo
ur computer connects to an IRC server at 
destination port 6667. The IRC server not only responds to your originating source port, but 
also sends an “identify” message to your computer on port 113. Using port triggering, you can 
tell the router, “When you initiate a session with destination port 6667, you have to also allow 
incoming traffic on port 113 to reach the originating computer.” Using steps similar to the 
preceding example, the following sequence shows the effects of the port triggering rule you 
have defined:
1. Y
ou open an IRC client program to start a chat session on your computer. 
2.Y
our IRC client composes a request message to an IRC server using a destination port 
number of 6667, the standard port number for an IRC server process. Your computer then 
sends this request message to your router.
3. Y
our router creates an entry in its internal session table describing this communication 
session between your computer and the IRC server. Your router stores the original 
information, performs Network Address Translation (NAT) on the source address and port, 
and sends this request message through the Internet to the IRC server. 
4. Noting 
your port triggering rule and having observed the destination port number of 6667, 
your router creates an additional session entry to send any incoming port 113 traffic to your 
computer.
5. Th
e IRC server sends a return message to your router using the NAT-assigned source port 
(as in the previous example, say port 33333) as the destination port. The IRC server also 
sends an “identify” message to your router with destination port 113.
6. Upon receiving the 
 incoming message to destination port 33333, your router checks its 
session table to determine whether there is an active session for port number 33333. 
Finding an active session, the router restores the original address information replaced by 
NAT and sends this reply message to your computer.
7. Upon receiving the incoming 
 message to destination port 113, your router checks its session 
table and learns that there is an active session for port 113, associated with your computer. 
The router replaces the message’s destination IP address with your computer’s IP address 
and forwards the message to your computer.
8. Wh
en you finish your chat session, your router  eventually senses a period of inactivity in the 
communications. The router then removes the session information from its session table, 
and incoming traffic is no longer accepted on port numbers 33333 or 113.
To configure port triggering, you need to  know which in
 bound ports the application needs. 
Also, you need to know the number of the outbound port that will trigger the opening of the 
inbound ports. You can usually determine this information by contacting the publisher of the 
application or user groups or newsgroups.
Note: Only one computer at a time can use the triggered application.
Port Forwarding to Permit External Host Communications
In both of the preceding examples, your com puter initiates an application session with a 
server computer on the Internet. However, you might need to allow a client computer on the  
						

							Advanced Settings95
 N900 Wireless Dual Band Gigabit Router WNDR4500
Internet to initiate a connection to a server computer on your network. Normally, your router 
ignores any inbound traffic that is not a response to your own outbound traffic. You can 
configure exceptions to this default rule by using the port forwarding feature. 
A typical application of port forwarding can be shown by reversing the client-server 
re

lationship from the previous web server example. In this case, a remote computer’s 
browser needs to access a web server running on a computer in your local network. Using 
port forwarding, you can tell the router, “When you receive incoming traffic on port 80 (the 
standard port number for a web server process), forward it to the local computer at 
192.168.1.123.” The following sequence shows the effects of the port forwarding rule you 
have defined:
1. T
he user of a remote computer opens a browser and requests a web page from 
www.example.com, which resolves to the public  IP address of your router. The remote 
computer composes a web page request message with the following destination 
information: 
Destination address .
  The IP address of www.example.com, which is the address of your 
router.
Destination port number . 8
 0, which is the standard port number for a web server 
process.
The remote computer then sends this request message through the Internet to your 
ro
 uter.
2. Y
our router receives the request message and looks in its rules table for any rules covering 
the disposition of incoming port 80 traffic. Your port forwarding rule specifies that incoming 
port 80 traffic should be forwarded to local IP address 192.168.1.123. Therefore, your router 
modifies the destination information in the request message:
The destination address is replaced with 192.168.1.123.
Your router then sends this request message to your local network.
3. Y
our web server at 192.168.1.123 receives the request and composes a return message 
with the requested web page data. Your web se rver then sends this reply message to your 
router.
4. Y
our router performs Network Address Translation (NAT) on the source IP address, and 
sends this request message through the Internet to the remote computer, which displays the 
web page from www.example.com.
To configure port forwarding, you need to  know which in
 bound ports the application needs. 
You usually can determine this information by  contacting the publisher of the application or 
the relevant user groups and newsgroups.
How Port Forwarding Differs from Port Triggering
The following points summarize the differences between port forwarding and port triggering:
• Por
t triggering can be used by any computer on your network, although only one 
computer can use it at a time.
• Por
t forwarding is configured for a single computer on your network. 
						

							Advanced Settings96
N900 Wireless Dual Band Gigabit Router WNDR4500 
•
Port triggering does require that you know the computer’s IP address in advance. The IP 
address is captured automatically.
• Port forwarding requires that
  you specify the computer’s IP address during configuration, 
and the IP address can never change.
• Port triggerin
 g requires specific outbound traffic to open the inbound ports, and the 
triggered ports are closed after a period of no activity.
• Port forward
 ing is always active and does not need to be triggered.
Set Up Port Forwarding to Local Servers
Using the port forwarding feature, you can allow certain types of incoming traffic to reach 
servers on your local network. For example, you might want to make a local web server, FTP 
server, or game server visible and available to the Internet.
Use the Port Forwarding screen to configure the  route
 r to forward specific incoming protocols 
to computers on your local network. In addition to servers for specific applications, you can 
also specify a default DMZ server to which all other incoming protocols are forwarded.
Before starting, you need to determine which type of service, application, or game you want 
to pro
 vide, and the local IP address of the computer that will provide the service. The server 
computer has to always have the same IP address.
To set up port forwarding:
Tip:T
o ensure that your server computer always has the same IP address, 
use the reserved IP address feature of your N900 Wireless Dual Band 
Gigabit Router.  
						

							Advanced Settings97
 N900 Wireless Dual Band Gigabit Router WNDR4500
1.
Select  Advanced Setup > Port Forwarding/Port Triggering  to display the following 
screen:
Port Forwarding is selected as the service type.
2. From the  Service Name list, select 
 the service or game that you will host on your network. If 
the service does not appear in the list, see  Add a Custom Service on page 97 .
3. In the corresponding Server IP  Address fie
 ld, enter the last digit of the IP address of your 
local computer that will provide this service. 
4. Click  Add. T
 he service appears in the list in the screen.
Add a Custom Service
To define a service, game, or application that does not appear in the Service Name list, you 
have to first determine which port number or  range of numbers is used by the application. 
You can usually determine this information by  contacting the publisher of the application or 
user groups or newsgroups. 
To add a custom service:
1. Select  Advanced > Adva
 nced Setup > Port Forwarding/Port Triggering .
2. Select  Po
 rt Forwarding  as the service type. 
						

							Advanced Settings98
N900 Wireless Dual Band Gigabit Router WNDR4500 
3.
Click the Add Custom Service  button to display the following screen:
4.In the Service Name field, enter a descriptive name. 
5. In the Protoco l list, select the pro
 tocol. If you are unsure, select TCP/UDP.
6. In the Starting Port field, enter the beginning port number. 
• If the application uses a single port, enter the same port number in the Ending Port 
field.
• If the  application uses a range of ports, enter the ending port number of the range in 
the End
 ing Port field.
7. In the Server IP Address field, enter the IP ad dress of your local computer 
 that will provide 
this service.
8. Click  Apply . The service appe ars in 
 the list in the Port Forwarding/Port Triggering screen.
Editing or Deleting a Port Forwarding Entry
To edit or delete a port forwarding entry:
1.In the t able, select the radio button next to the service name.
2. Click  Edit Ser v
 ice or Delete Service .
Application Example: Making  a Local Web Server Public
If you host a web server on your local network , you can use port forwarding to allow web 
requests from anyone on the Internet to reach your web server. 
To make a local web server public:
1. Assign your  web server either 
 a fixed IP address or a dynamic  IP address using DHCP 
address reservation. In this example, your rout er will always give your web server an IP 
address of 192.168.1.33.  
						

							Advanced Settings99
 N900 Wireless Dual Band Gigabit Router WNDR4500
2.
In the Port Forwarding screen, configure the router to forward the HTTP service to the local 
address of your web server at  192.168.1.33. HTTP (port 80) is the standard protocol for web 
servers.
3. (Optional) Register a ho
 st name with a Dynamic DNS service, and configure your router to 
use the name as described in  Dynamic DNS on p
 age 101. To access your web server from 
the Internet, a remote user has to know the  I
 P address that has been assigned by your ISP. 
However, if you use a Dynamic DNS service, the remote user can reach your server by a 
user-friendly Internet name, such as mynetgear.dyndns.org.
Set Up Port Triggering
Port triggering is a dynamic extension of port forwarding that is useful in these cases:
• More t
han one local computer needs port forwarding for the same application (but not 
simultaneously).
• An 
application needs to open incoming ports that are different from the outgoing port.
When port triggering is enabled, the router moni tors outbo
 und traffic looking for a specified 
outbound “trigger” port. When the router detects outbound traffic on that port, it remembers 
the IP address of the local computer that sent the data. The router then temporarily opens the 
specified incoming port or ports, and forwards  incoming traffic on the triggered ports to the 
triggering computer. 
While port forwarding creates a static mapping of a port number or range to a single local 
computer
 , port triggering can dynamically open ports to any computer that needs them and 
can close the ports when they are no longer needed.
Note: If you use applications such as multiplayer gaming, peer-to-peer 
connections, real-time communicati ons such as instant messaging, 
or remote assistance (a feature in Windows XP), you should also 
enable Universal Plug and Play (UPnP) according to the instructions 
in Universal Plug and Play  on page 106.
To set up port triggering, you need to know which inb
 ound ports the application needs. Also, 
you need to know the number of the outbound port that will trigger the opening of the inbound 
ports. You can usually determine this inform ation by contacting the publisher of the 
application or user groups or newsgroups.
To set up port triggering: 
1. Select  Adv
 anced > Advanced Setup > Port Forwarding/Port Triggering . 
						

							Advanced Settings100
N900 Wireless Dual Band Gigabit Router WNDR4500 
2.
Select the  Port Triggering  radio button to display the port triggering information.
3.Clear the  Disable Port Triggering  check box if it is selected.
Note:  If the Disable Port Triggering check box is selecte d
  after you configure 
port triggering, port triggering is disabled. However, any port triggering 
configuration information you added to the router is retained even though it is 
not used.
4. In the Port Triggering Timeout field, enter a value up to 9999 minutes. 
5. This value controls the inactivity timer for the designated inbound ports. The inbound ports 
close wh
 en the inactivity time expires. This is required because the router cannot be sure 
when the application has terminated.