Configuring SIP, SPCP, and NAT
Network Address Translation (NAT) and Cisco IP Phones
Cisco SPA 500 Series and WIP310 IP Phone Administration Guide
105
4
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, page 105
•
NAT Mapping with SIP-ALG Router, page 105
•
Configuring NAT Mapping with a Static IP Address, page 105
•
Configuring NAT Mapping with STUN, page 106
NAT Mapping with Session Border Controller
It is strongly recommended that you choose an ITSP that supports NAT mapping
through a Session Border Controller. With NAT mapping provided by the ITSP, you
have more choices in selecting a router.
NAT Mapping with SIP-ALG Router
If the ITSP network does not provide a Session Border Controller functionality, you
can achieve NAT mapping by using a router that has a SIP ALG (Application Layer
Gateway). By using a SIP-ALG router, you have more choices in selecting an ITSP.
Configuring NAT Mapping with a Static IP Address
If the ITSP network does not provide a Session Border Controller functionality, and
if other requirements are met, you can configure NAT mapping to ensure
interoperability with the ITSP.
Requirements
•
You must have an external (public) IP address that is static.
•
The NAT mechanism used in the router must be symmetric. See
“Determining
Whether the Router Uses Symmetric or Asymmetric NAT,” on page 108
.
NOTE
Use NAT mapping only if the ITSP network does not provide a Session Border
Controller functionality.
