Nat Mapping With Stun - Cisco SPA301 Administration Manual

Configuring SIP, SPCP, and NAT
Managing NAT Transversal with Cisco IP Phones
STEP 6
STEP 7
STEP 8
STEP 1
STEP 2
Cisco Small Business SPA300 Series, SPA500 Series, and WIP310 IP Phone Administration Guide
(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.
Click Submit All Changes.
Configure the firewall settings on your router to allow SIP traffic. See
SIP.

NAT Mapping with STUN

If the service provider network does not provide a Session Border Controller
functionality and if the other requirements are met, it is possible to use Session
Traversal Utilities for NAT (STUN) to discover the NAT mapping. The STUN
protocol allows applications operating behind a network address translator (NAT)
to discover the presence of the network address translator and to obtain the
mapped (public) IP address (NAT addresses) and the port number that the NAT
has allocated for the User Datagram Protocol (UDP) connections to remote hosts.
The protocol requires assistance from a third-party network server (STUN server)
located on the opposing (public) side of the NAT, usually the public Internet. This
option is considered a last resort and should be used only if the other methods are
not available. To use STUN
• The router must use asymmetric NAT. See
Uses Symmetric or Asymmetric
• A computer running STUN server software is available on the network. You can
also use a public STUN server or set up your own STUN server.
Click Voice > SIP and navigate to NAT Support Parameters.
Set the following parameters to yes:
• Handle VIA received
• Insert VIA received,
• Substitute VIA Addr
• Handle VIA rport
• Insert VIA rport
Determining Whether the Router
NAT.
4
Configuring
143