Cisco Systems manual Using the SPA9000 with a Firewall or Router, SPA400 SIP-PSTN Gateway

Chapter 1 Using the Linksys Voice System

Technology Background

Local traffic is not affected by this configuration. When UserA initiates a call to UserB, RTP traffic still flows directly between the two UAs. The media proxy only affects RTP traffic to a UA connected through the ITSP.

Using the SPA9000 with a Firewall or Router

When using the SPA9000 behind a firewall or router, make sure that the following ports are not blocked:

•SIP ports—By default, UDP port 5060 and 5061

•RTP ports—16384 to 16482

Also disable SPI if this function exists on your firewall.

SPA400 SIP-PSTN Gateway

When a local user on the SPA9000 network initiates a call to a PSTN subscriber, the SPA400 acts as the SIP-PSTN gateway, which converts the SIP and RTP media packets into the appropriate signal for transmission to the PSTN switch. For example, if UserA calls UserD, the SIP request is routed by the SIP proxy in the SPA9000 to the SPA400 (see Figure 1-4).

Figure 1-4 The SPA400 as a SIP-PSTN Gateway

			PSTN
	UserD
				1 to 4 DID lines
				SPA400
		UserB		SIP-PSTN
				Gateway
UserA

Switch

Internet (WAN) Interface

SPA9000

SIP Proxy

The SPA400 then converts the SIP and RTP packets it receives from UserA and the signals it receives from the PSTN switch.

	Linksys SPA9000 Administrator Guide
1-8	Document Version 3.01