Prerequisite Tasks

Before you can configure your router to use VoIP, you need to perform the following tasks:

• Establish a working IP network. For more information about configuring IP, refer to the "IP Overview," "Configuring IP Addressing," and "Configuring IP Services" chapters in the Network Protocols Configuration Guide, Part 1 for Cisco IOS Release 12.0T.


• Install the voice interface cards (VICs) in your router. For more information about installing a VIC in your router, refer to the Cisco WAN Interface Cards Hardware Installation Guide.


• Complete your company's dial plan.


• Establish a working telephony network based on your company's dial plan.


• Integrate your dial plan and telephony network into your existing IP network topology. Merging your IP and telephony networks depends on your particular IP and telephony network topology. In general, we recommend the following:
  
  1. Use canonical numbers wherever possible. Avoid situations where numbering systems are significantly different on different routers or access servers in your network.
  
  2. Make routing and dialing transparent to the user—for example, avoid secondary dial tones from secondary switches, where possible.
  
  3. Contact your PBX vendor for instructions about how to reconfigure the appropriate PBX interfaces.
  After you have analyzed your dial plan and decided how to integrate it into your existing IP network, you are ready to configure your network devices to support VoIP.