On Networks N150RM User Manual - Manual (Page 37)

Security Settings
37
N150 Wireless ADSL2+ Modem Router N150RM
Block Services
Services are functions performed by server computers at the request of client computers. For
example, web servers serve web pages, time servers serve time and date information, and
game hosts serve data about other players’ moves. When a computer on the Internet sends
a request for service to a server computer, the requested service is identified by a service or
port number. This number appears as the destination port number in the transmitted IP
packets. For example, a packet that is sent with destination port number 80 is an HTTP (web
server) request.
The service numbers for many common protocols are defined by the Internet Engineering
Task Force (IETF at
http://www.ietf.org/ ) and published in RFC1700, “Assigned Numbers.”
Service numbers for other applications are typically chosen from the range 1024 to 65535 by
the authors of the application. Although the modem router already holds a list of many
service port numbers, you are not limited to these choices.
 To add your own service definitions:
1. Select Security > Services to display the following screen:
2. Click the Add Services button. If you want to change a service, select it and click Edit
Service
.
3.
Define or edit a service by specifying the following.
• Name
. Enter a meaningful name for the service.
• Type . Select the correct type for this service. If in doubt, select TCP/UDP. The options
are TCP, UDP, and TCP/UDP.
• Start Port and Finish Port. If a port range is required, enter the range here. If a single
port is required, enter the same value in both fields.
4. Click Apply to save your changes.
Firewall Rules to Control Network Access
Your modem router has a firewall that blocks unauthorized access to your wireless network
and permits authorized inbound and outbound communications. Authorized communications
are established according to inbound and outbound rules. The firewall has the following two
default rules. You can create custom rules to further restrict the outbound communications or
more widely open the inbound communications:
• Inbound . Block all access from outside except responses to requests from the LAN side.
• Outbound . Allow all access from the LAN side to the outside.