Chapter 3: Routing Calls over Analog Voice Ports

Cisco Press

  • Describe the various call types in a VoIP network.

  • Configure analog voice interfaces as new devices are introduced into the voice path.

  • Configure dial peers so you can add call routing intelligence to a router.

Voice gateways bridge the gap between the VoIP world and the traditional telephony world (for example, a private branch exchange [PBX], the public switched telephone network {PSTN], or an analog phone). Cisco voice gateways connect to traditional telephony devices via voice ports. This chapter introduces basic configuration of analog and digital voice ports and demonstrates how to fine-tune voice ports with port-specific configurations. Upon completing this chapter, you will be able to configure voice interfaces on Cisco voice-enabled equipment for connection to traditional, nonpacketized telephony equipment.

Introducing Analog Voice Applications on Cisco IOS Routers

Before delving into the specific syntax of configuring voice ports, this section considers several examples of voice applications. The applications discussed help illustrate the function of the voice ports, whose configuration is addressed in the next section.

Different types of applications require specific types of ports. In many instances, the type of port is dependent on the voice device connected to the network. Different types of voice applications include the following:

  • Local calls

  • On-net calls

  • Off-net calls

  • Private line, automatic ringdown (PLAR) calls

  • PBX-to-PBX calls

  • Intercluster trunk calls

  • On-net to off-net calls

The following sections discuss each in detail and provide an example.

Local Calls

Local calls, as illustrated in Figure 3-1, occur between two telephones connected to one Cisco voice-enabled router. This type of call is handled entirely by the router and does not travel over an external network. Both telephones are directly connected to Foreign Exchange Station (FXS) ports on the router.

Figure 3-1

Local Calls

An example of a local call is one staff member calling another staff member at the same office. This call is switched between two ports on the same voice-enabled router.

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