Cisco Linksys SPA9000 - Manual (Page 33)

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Linksys SPA9000 Administrator Guide
Document Version 3.01
Chapter 2 Getting Started
Implementing LVS
In addition, you need at least one active ITSP phone service account and its settings (including DID
number for incoming calls) if you use the Internet for telephone service. If you are using the SPA400 for
connection to the PSTN, you need at least one active PSTN line.
The LVS can also be implemented with hosted voicemail services provided by the ITSP. In this scenario,
the SPA-400 is not configured for voicemail, but is only used for as a SIP-PSTN gateway, providing
telephone connectivity to PSTN subscribers.
Note For first-time installation of the SPA9000, it is recommended that you use the SPA9000 Setup Wizard,
which you can download from www.linksys.com. For further information, see
“Using the Wizard for
Initial Configuration” section on page 2-13 .
Using the SPA9000 as a Media Proxy
The SPA9000 can act as a media proxy, which means that all RTP traffic between local client stations
and client stations on the Internet are routed through the SPA9000. This simplifies firewall configuration
because only the SPA9000 requires access to the Internet through the firewall.
By default, the SPA9000 acts only as a SIP proxy. This means that once a SIP connection is established,
further communication between the SIP UAs occurs directly. To enable the SPA9000 as a media proxy,
set the PBX Parameters:<Force Media Proxy> parameter to yes.
Using the LVS as a Key System
An easy and cost-effective way to implement the SPA9000 is as a replacement of a legacy key system,
in which a single DID line from the PSTN supports a single extension. In a key system all lines appear
as shared lines. This allows a user to pick up a ringing line from any phone in the key system (see
Figure 2-2 ).