Polycom EX Manual De Usuario

Chapter 4 - Installing Videoconferencing Systems

© Polycom, Inc.

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A firewall protects an organization’s network by controlling data 
traffic from outside the network. Different types of firewalls use 
different techniques to provide network security, but unless the 
firewall is designed to work with H.323 videoconferencing 
equipment, it will prevent successful videoconferencing because it 
is designed to prevent unsolicited data from entering the network. 
From a functional perspective, it blocks incoming calls, and it 
prevents outgoing calls by blocking the call signalling from the 
external endpoint when the two endpoints begin the signal 
transaction required to set up the call.

Network Address Translation (NAT) network environments use 
internal IP addresses for the devices within the network, while 
using one external IP address to communicate with the outside 
world (Wide Area Network). The NAT router accepts incoming data 
and forwards it to the appropriate endpoint. This provides a degree 
of network security, as the internal IP addresses do not provide 
access from outside the network. 

Firewalls and NAT are often used together.

To make calls through a firewall, you must open the following ports 
and assign them to the videoconferencing system:

Table 4-1.  Firewall Ports to Open for Videoconferencing

389 (TCP)

ILS registration

1503 (TCP)

Microsoft NetMeeting T.120 data sharing

1718 (UDP)

Gatekeeper discovery

1719 (UDP)

Gatekeeper RAS (must be bidirectional)

1720 (TCP)

H.323 call set-up (must be bidirectional)

1731 (TCP)

Audio call control (must be bidirectional)

3230-3235 
(TCP/UDP)

Signalling and control for audio, call, video, and 
data/FECC

3603 (TCP)

Web interface