19216811.liveSecurity
31
Wireless Cable Voice Gateway CG3700EMR-1CMNDS
2.
In the Trusted IP Address field, enter the IP address.
3.
Click the
Apply
button.
Your changes are saved.
Block Services (Port Filtering)
Server computers perform services 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 players’ moves. When a computer on the Internet sends a request for
service to a server computer, a service or port number identifies the requested service. This
number displays as the destination port number in the transmitted IP packets. For example, a
packet that is sent with the 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
) and published in RFC1700, “Assigned Numbers.”
Service numbers for other applications are typically chosen from the range 1024–65535 by
the authors of the application. Although the gateway already holds a list of many service port
numbers, you are not limited to these choices. You can often find port number information by
contacting the publisher of the application, by asking user groups or newsgroups, or by
searching.
The Block Services screen lets you add and block specific Internet services by computers on
your network. This capability is called service blocking or port filtering. To add a service for
blocking, first find out which port number or range of numbers the application uses.
To block services:
1.
Select
ADVANCED > Security > Block Services
.
2.
Select either
the
Per Schedule
or
Always
radio button.
3.
If you selected Per Schedule, specify a time period in the Schedule screen.
For more information see
Schedule Blocking
on page
32.