Netgear Dgn2200v4 N300 Wireless Adsl2 Plus Modem Router User Manual

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Port Triggering to Open Incoming Ports
Some application servers (such as FTP and IRC servers) send replies to multiple port 
numbers. Using the port triggering function of your modem router, you can tell the modem 
router to open more incoming ports when a particular outgoing port originates a session.
An example is Internet Relay Chat (IRC). Your 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 modem 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. You open an IRC client program to start a chat session on your computer. 
2. Your 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 modem router.
3. Your modem router creates an entry in its internal session table describing this 
communication session between your computer and the IRC server. Your modem 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 modem router creates an additional session entry to send any incoming port 113 traffic 
to your computer.
5. The IRC server sends a return message to your modem router using the NAT-assigned 
source port (for example, port 33333) as the destination port. The IRC server also sends an 
“identify” message to your modem router with destination port 113.
6. Upon receiving the incoming message to destination port 33333, your modem router 
checks its session table to determine whether there is an active session for port number 
33333. Finding an active session, the modem 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 modem router checks 
its session table and learns that there is an active session for port 113, associated with your 
computer. The modem router replaces the message’s destination IP address with your 
computer’s IP address and forwards the message to your computer.
8. When you finish your chat session, your modem router eventually senses a period of 
inactivity in the communications. The modem 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 inbound 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 the relevant user groups or news groups. 
						

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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 computer initiates an application session with a 
server computer on the Internet. However, you might need to allow a client computer on the 
Internet to initiate a connection to a server computer on your network. Normally, your modem 
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 
relationship 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 modem 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 
192.168.0.123.” The following sequence shows the effects of the port forwarding rule you 
have defined:
1. The 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 modem 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 
modem router.
Destination port number. 80, which is the standard port number for a web server 
process.
The remote computer then sends this request message through the Internet to your 
modem router.
2. Your modem 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 192.168.0.123. Therefore, 
your modem router modifies the destination information in the request message:
The destination address is replaced with 192.168.0.123.
Your modem router then sends this request message to your local network.
3. Your web server at 192.168.0.123 receives the request and composes a return message 
with the requested web page data. Your web server then sends this reply message to your 
modem router.
4. Your modem 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 inbound ports the application needs. 
You usually can determine this information by contacting the publisher of the application or 
the relevant user groups or news groups. 
						

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How Port Forwarding Differs from Port Triggering
The following points summarize the differences between port forwarding and port triggering:
•Port triggering can be used by any computer on your network, although only one 
computer can use it at a time.
•Port forwarding is configured for a single computer on your network.
•With port triggering, the modem router does not need to 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 triggering requires specific outbound traffic to open the inbound ports, and the 
triggered ports are closed after a period of no activity.
•Port forwarding is always active and does not need to be triggered.
Set Up Port Forwarding to Local Servers
The port forwarding feature lets you 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/Port Triggering screen to configure the modem router 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 you start, determine which type of service, application, or game you want to provide, 
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 ensure that your server computer always has the same IP address, use the reserved IP 
address feature of your product. See 
Address Reservation on page 42. 
						

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To forward specific incoming protocols:
1. 
Select  Advanced > 
 Advanced Setup > Port Forwarding/Port Triggering .
2. From the Service Name list, select the service or game that you will hos\
t on your network. 
If the service does not appear in the list, see  Add a Custom Service on page
  64.
3.  In the 
Action list, select when you want to allow or block this port forwarding\
 rule.
4. In the Server IP 
 Address field, enter IP address of your local computer that will receive\
 the 
inbound traffic covered by this rule.
5.  In the W
 AN Servers field, fill in the IP addresses covered by this rule.
6.  In the Log list, select Never or  Always to specify when to log packets covered by this rule.
7.  Click  Add. 
The service appears in the list on the Port Forwarding screen.
Add a Custom Service
To define a service, game, or application that does not appear in the Ser\
vice Name list, first 
determine which port number or range of numbers the application uses. You can usually 
determine this information by contacting the publisher of the applicatio\
n or user groups or 
news groups. When you have the port number information, follow these ste\
ps.
To add a custom service:
1.  Select  Advanced > 
 Advanced Setup > Port Forwarding/Port Triggering .
2.  Select the  Port Forwarding radio button as the service type. 
						

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3. 
Click the  Add Custom Service button.
4. In the Name field, enter a descriptive name. 
5.  In the Service 
 Type list, select the protocol. If you are unsure, select  TCP/UDP.
6.  In the External and Internal Starting Port fields, enter the beginning p\
ort number
 . 
• If the service uses only one port, enter the port number in the Ending P\
ort field.
• If the service uses a range of ports, enter the end port number in the E\
nding Port field.
7.  In the Internal IP 
 Address field, enter the IP address of your local computer that will pro\
vide 
this service.
8.  Click  Apply . 
The service appears in the list in the Port Forwarding/Port Triggering screen.
Edit or Delete a Port Forwarding Entry
To edit or delete a port forwarding entry:
1.  In the table, select the radio button next to the service name.
2.  Click  Edit Service or  Delete Service.
Application Example: Make a Local Web Server Public
If you host a web server on your local network, you can use port forward\
ing 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 modem router always gives your web server an IP ad\
dress of 
192.168.0.33. 
2.  In the Port Forwarding/Port 
 Triggering screen, configure the  modem router to forward the 
HTTP service to the local address of your web server at  192.168.0.33. 
HTTP (port 80) is the standard protocol for web servers. 
						

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3. (Optional) Register a host name with a Dynamic DNS service, and configure your modem 
router to use the name. 
To access your web server from the Internet, a remote user has to know the IP address 
that your ISP assigned. 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 than 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 modem router monitors outbound traffic looking for a 
specified outbound “trigger” port. When the modem router detects outbound traffic on that 
port, it remembers the IP address of the local computer that sent the data. The modem router 
then temporarily opens the specified incoming port or ports and forwards incoming traffic on 
the triggered ports to the triggering computer. 
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 communications such as instant messaging, or 
remote assistance (a feature in Windows XP), you should also enable 
Universal Plug and Play (UPnP).
To configure port triggering, you need to know which inbound ports the application needs, 
and 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 news groups.
To enable port triggering: 
1. Select Advanced > Port Forwarding/Port Triggering. 
						

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2. 
Select the Port Triggering  radio button.
3. Clear the Disable Port Triggering check box.
Note: If the Disable Port Triggering check box is selected after you 
configure port triggering, port triggering is disabled. However, any port 
triggering configuration information you added to the modem router is 
retained even though it is not used.
4.  In the Port 
 Triggering Timeout field, enter a value up to 9999 minutes. 
This value controls the inactivity timer for the designated inbound port\
s. The inbound  ports close when the inactivity time expires. 
 This is required because the modem router 
cannot detect when the application has terminated.
To add a port triggering service:
1.  On the Port 
 Triggering screen, click  Add Service.
2. In the Service Name field, type a descriptive service name. 
3.  In the Service User list, select  Any or Single address and enter the IP address of one 
computer
 .
• Any (the default), allows any computer on the Internet to use this ser\
vice. 
• Single address restricts the service to a particular computer
 .  
						

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4. Select the service type, either TCP or UDP or both (TCP/UDP). If you are not sure, select 
TCP/UDP.
5. In the Triggering Port field, enter the number of the outbound traffic port that will cause the 
inbound ports to be opened. 
6. Enter the inbound connection port information in the Connection Type, Starting Port, and 
Ending Port fields.
7. Click Apply.
The service appears in the Port Triggering Portmap Table. 
8. Make sure that you enable port triggering so that the service that you added will be used. 
						

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Schedule When to Block the Internet
You can specify the days and time that you want to block Internet access.\
To schedule blocking:
1. 
Select  Advanced > Security > Schedule .
2. Set up the schedule for blocking keywords and services.
• Days to Block . Select days on which you want to apply blocking by selecting the 
appropriate check boxes, or select Every Day to select the check boxes for all days. 
• T
ime of Day to Block. Select a start and end time in 24-hour format, or select  All 
Day for 24-hour blocking. 
3.  Select your time zone from the list. If you use daylight savings time, s\
elect the 
Automatically adjust for daylight savings time  check box. 
4.  Click  Apply . 
Your settings are saved. 
						

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Security Event Email Notifications
To receive logs and alerts by email, provide your email information in th\
e E-mail screen, and 
specify which alerts you want to receive and how often. 
To set up email notifications:
1.  Select  Advanced > Security >  E-mail.
2. Select the  Turn Email Notification On  check box.
3.  In the 
Your Outgoing Mail Server field, enter the name of your ISP’s outgoing (SMTP) mail 
server (such as mail.myISP.com). 
You might be able to find this information in the configuration screen of\
 your email  program. If you leave this field blank, log and alert messages are not s\
ent.
4.  Enter the email address to which logs and alerts are sent in the Send to\
 
 This Email Address 
field. 
This email address is also used for the From address. If you leave this \
field blank, log and  alert messages are not sent.
5.  If your outgoing email server requires authentication, select the  My Mail Server requires 
authentication  check box. Fill in the User Name and Password fields for the outgoing e\
mail 
server

.
6.  (Optional) Select the  Send Alerts 
 Immediately check box.
Email alerts are sent immediately when someone attempts to visit a block\
ed site.
7.  (Optional) Fill in the fields in the Send logs according to this sched\
ule section of the screen.
Logs are sent automatically. If the log fills up before the specified time, the log is emailed. 
After the log is sent, the log is cleared from the modem router memory
 . If the modem 
router cannot email the log file, the log buffer might fill up. In this case, the modem router 
overwrites the log and discards its contents.
8.  Click  Apply .