Cisco 8841 Administration Guide

Step 3 Click Submit All Changes.
NAT Mapping with Session Border Controller
We recommend that you choose an service provider that supports NAT mapping through a Session Border
Controller. With NAT mapping provided by the service provider, you have more choices in selecting a router.
NAT Mapping with SIP-ALG Router
NAT mapping can be achieved by using a router that has a SIP Application Layer Gateway (ALG). By using
a SIP-ALG router, you have more choices in selecting an service provider.
NAT Mapping with the Static IP Address
You can configure NAT mapping on the phone to ensure interoperability with the service provider.
• You must have an external (public) IP address that is static.
• The NAT mechanism used in the router must be symmetric. For more information, see Determining
Symmetric or Asymmetric NAT, on page 70 .
Use NAT mapping only if the service provider network does not provide a Session Border Controller
functionality.
Before you begin
Access the phone administration web page. See Access the Phone Web Page, on page 88.
Procedure
Step 1 Select Voice > SIP.
Step 2 In the NAT Support Parameters section, set Handle VIA received, Insert VIA received, Substitute VIA
Addr, Handle VIA rport, Insert VIA rport, and Send Resp To Src Port fields to Yes.
Step 3 In the NAT Support Parameters section, set a value for the NAT Keep Alive Intvl field.
Step 4 Enter the public IP address for your router in the EXT IP field.
Step 5 Click the Ext(n) tab.
Step 6 In the NAT Settings section, set NAT Mapping Enable to Yes.
Step 7 (Optional) Set NAT Keep Alive Enable to Yes.
The service provider might require the phone to send NAT keep alive messages to keep the NAT ports open.
Check with your service provider to determine the requirements.
Step 8 Click Submit All Changes.
What to do next
Configure the firewall settings on your router to allow SIP traffic.
Cisco IP Phone 8800 Series Multiplatform Phones Administration Guide
69
Cisco IP Phone Installation
NAT Mapping with Session Border Controller

Cisco 8841 Specifications

General

Brand	Cisco
Model	8841
Category	IP Phone
Language	English