Introduction; Audience; Scope; Related Documents - Cisco SPA8800 Configuring

Configuring the Cisco SPA8800 IP Telephony Gateway in an Asterisk Environment

Introduction

®
The Cisco SPA8800 IP Telephony Gateway provides four RJ-11 FXS and four FXO ports, a
10/100BASE-T RJ-45 Ethernet interface to connect to either a router or multilayer switch, and an
auxiliary port for local administration. It also provides a single multiport RJ-21 50-pin connector.
®
The SPA8800 can in only a matter of minutes, be easily be configured as an Asterisk FXO
gateway.
Calls originating from the public switched telephone network (PSTN) can be terminated by the
SPA8800's FXO ports and routed to analog or IP phones based on an Asterisk server's
configuration. Analog phones connected to the SPA8800 can make low-cost VoIP calls via an
Internet Telephony Service Provider (ITSP) or can make calls via the PSTN.
Many interesting call routing options are possible using Asterisk to control the SPA8800 gateway.
Asterisk can be configured to trunk the SPA8800's four FXO ports together into a trunk group. A
trunk group allows the PSTN lines connected to the FXO ports to be over-subscribed and shared
among all configured analog and IP phones, effectively lowering telephony costs by not requiring a
dedicated line per phone. For example, you can have 4 connected PSTN lines and share them with
th
any number of phones. When all 4 lines are busy, the 5 user will hear a congestion tone.
Additionally, the SPA8800's FXS ports can be used in other ways, including connecting analog
phones, door phones, and fax machines.
The SPA8800 supports fax with G.711 pass-through or real-time fax over IP via T.38 fax relay and
also supports the G.711 A-law, G.711 µ-law, G.726, G.729A, G.723.1 voice codecs.
In the event that you only need FXS ports and do not need any FXO ports, consider using the
Cisco SPA8000 8-Port IP Telephony Gateway. The SPA8000 configuration is very similar to the
SPA8800.

Audience

This application note is targeted at anyone who needs an FXO gateway for their Asterisk server. It
is expected that readers of this document are familiar with the administration tasks involved with
configuring VoIP in an Asterisk environment.

Scope

This scope of this document is limited to configuring the SPA8800 in an Asterisk environment and
does not address the following topics:
• Installing an Asterisk server
• Advanced Asterisk configuration
• SPA8800 localization
• Security
Refer to the Related Documents for additional configuration and background information.

Related Documents

• Asterisk:
http://www.asterisk.org
• Asterisk Book from O'Reilly:
http://www.asteriskdocs.org/
• Cisco SPA8800 Administration Guide
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