Cisco SPA2102-SF Administration Guide - Page 47

3 Configuring Your System for ITSP Interoperability This chapter provides configuration details to help you to ensure that your infrastructure properly supports voice services. • "Network Address Translation (NAT) and Voice over IP (VoIP)," on page 47 • "Firewalls and SIP," on page 53 • "Configuring SIP Timer Values," on page 53 Network Address Translation (NAT) and Voice over IP (VoIP) NAT is a function that allows multiple devices to share the same public, routable, IP address to establish connections over the Internet. NAT is present in many broadband access devices to translate public and private IP addresses. To enable VoIP to co-exist with NAT, some form of NAT traversal is required. Some ITSPs provide NAT traversal, but some do not. If your ITSP does not provide NAT traversal, you have several options. • "NAT Mapping with Session Border Controller," on page 48 • "NAT Mapping with SIP-ALG Router," on page 48 • "Configuring NAT Mapping with a Static IP Address," on page 48 • "Configuring NAT Mapping with STUN," on page 50 Cisco Small Business ATA Administration Guide 47