Cisco WRP400-G1 Administration Guide - Page 23

2 Configuring Your System for ITSP Interoperability This chapter provides configuration details to help you to ensure that your infrastructure properly supports voice services. • "Configuring NAT Mapping," on page 21 • "Firewalls and SIP," on page 26 • "Configuring SIP Timer Values," on page 27 Configuring NAT Mapping As discussed in Chapter 1, "Product Overview and Deployment Guidelines," some form of NAT mapping is needed to support VoIP. If your ITSP does not support NAT mapping through a Session Border Controller, and your edge device is not a SIP-ALG router, you can address this issue through one of the following methods: • "Configuring NAT Mapping with a Static IP Address," on page 21 • "Configuring NAT Mapping with STUN," on page 23 Configuring NAT Mapping with a Static IP Address This option can be used if the following requirements are met: • You must have a static external (public) IP address from your ISP. • The edge device-that is, the router between your local area network and your ISP network-must have a symmetric NAT mechanism. If the WRP400 is the edge device, this requirement is met. If another device is used as the edge device, see "Determining Whether the Router Uses Symmetric or Asymmetric NAT," on page 25. Cisco Small Business WRP400 Administration Guide 21