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Linksys SPA9x2 Phone Administration Guide Cisco Confidential--First Draft12
Network Address Translation and SPA9x2 Phones
Introducing Linksys SPA9x2 Phones
• ”Session Border Controllers” section on page 12
• ”Simple Traversal of UDP Through NATs (STUN)” section on page 13
• ”SIP-NAT Interoperation” section on page 13
• ”Determining the Type of NAT Used on Your Router” section on page 14
Routers and Service Provider Support of NAT
NAT allows multiple devices to share the same public, routable, IP address for establishing
connections over the Internet. A router forwards packets between the Internet and the internal,
private network.
NAT mapping is the association between a private address and port and a public address and
port . The mapping is maintained for a short period of time, varying from a few seconds to
several minutes. The mapping time is extended when a source device sends a packet.
Session Border Controllers
The service provider can support NAT mapping using a session border controller. With a session
border controller, you do not have to manage NAT on the SPA9x2.
If the service provider does not support session border control, use the NAT Support
Parameters provided by the SPA9x2, such as:
•Outbound Proxy (see ”Proxy and Registration Parameters” section on page 100)
• STUN Server Enable (see ”NAT Support Parameters” section on page 52)
•EXT IP