ZyXEL Communications ISG50 User Manual

ISG50 User’s Guide

This chapter shows you how to set up your ISG50-wide PBX settings including SIP server, feature 
code, email, fake IP, peer to peer, QoS and TAPI settings. 

The following diagram shows SIP devices communicating with the ISG50. In SIP some devices act 
as clients and others as servers. For example, in the figure below, devices A-D act as clients and 
must register with the ISG50 before they are able to make calls via the ISG50. The ISG50 also is a 
client in relation to the SIP server located at the ITSP (F). The ISG50 must register with the ITSP 
SIP server before calls can be routed to telephones outside its network. Finally, two SIP servers can 
act as peers, as shown with another ISG50 (E) in the figure below. In this case, both ISG50s must 
register with each other before they can forward each other’s calls.

SIP Devices and the ISG50 

• Use  the  SIP Server screen to configure ISG50’s general SIP server settings. See 

.

• Use  the  Feature Code screen to configure feature code settings. It allows users to dial a code on 

their phone’s keypad to enable or disable a feature your ISG50 supports. See 

.

• Use  the  E-Mail screen to configure email settings. It allows users to send voice mails or CDR 

backup data through the email server. See 

• Use  the  Fake IP screen to configure settings that may help you to avoid any potential VoIP 

problems that result from having the ISG50 behind a NAT router. See