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Network Address Translation (NAT)
11.1 Overview
This chapter discusses how to configure NAT on the VMG. NAT (Network Address Translation - NAT,
RFC 1631) is the translation of the IP address of a host in a packet, for example, the source address
of an outgoing packet, used within one network to a different IP address known within another
network.
11.1.1 What You Can Do in this Chapter
• Use the Port Forwarding screen to configure forward incoming service requests to the server(s)
on your local network
• Use the Port Triggering screen to add and configure the VMG's trigger port settings
11.3 on page
• Use the DMZ screen to configure a default server
• Use the ALG screen to enable and disable the NAT and SIP (VoIP) ALG in the VMG
on page
162).
• Use the Sessions screen to configure the VMG's maximum number of NAT sessions
11.6 on page
11.1.2 What You Need To Know
Inside/Outside
Inside/outside denotes where a host is located relative to the VMG, for example, the computers of
your subscribers are the inside hosts, while the web servers on the Internet are the outside hosts.
Global/Local
Global/local denotes the IP address of a host in a packet as the packet traverses a router, for
example, the local address refers to the IP address of a host when the packet is in the local
network, while the global address refers to the IP address of the host when the same packet is
traveling in the WAN side.
NAT
In the simplest form, NAT changes the source IP address in a packet received from a subscriber
(the inside local address) to another (the inside global address) before forwarding the packet to the
WAN side. When the response comes back, NAT translates the destination address (the inside
global address) back to the inside local address before forwarding it to the original inside host.
VMG5313-B10A/-B30A Series User's Guide
(Section 11.2 on page
159).
162).
C
HAPTER
156).
(Section 11.4 on page
11
(Section
161).
(Section 11.5
(Section
155
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