ZyXEL Communications NBG-417N, Руководство пользователя, Страница: 125 / 279

Chapter 11 NAT
User
’
s Guide
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11.1.1 What You Can Do in this Chapter
• Use the General ( Section 11.2 on page 128 ) screen to enable NAT and set a
default server.
• Use the Application ( Section 11.3 on page 129 ) screen to change your
NBG4115 ’ s port forwarding settings.
• Use the Advanced ( Section 11.5.3 on page 133 ) screen to change your
NBG4115 ’ s trigger port settings.
11.1.2 What You Need To Know
The following terms and concepts may help as you read through this chapter.
Inside/Outside
This denotes where a host is located relative to the NBG4115, for example, the
computers of your subscribers are the inside hosts, while the web servers on the
Internet are the outside hosts.
Global/Local
This 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.
Note: Inside/outside refers to the location of a host, while global/local refers to the IP
address of a host used in a packet.
An inside local address (ILA) is the IP address of an inside host in a packet when
the packet is still in the local network, while an inside global address (IGA) is the
IP address of the same inside host when the packet is on the WAN side. The
following table summarizes this information.
Note: NAT never changes the IP address (either local or global) of an outside host.
Table 45 NAT Definitions
ITEM DESCRIPTION
Inside This refers to the host on the LAN.
Outside This refers to the host on the WAN.
Local This refers to the packet address (source or destination) as the packet travels
on the LAN.
Global This refers to the packet address (source or destination) as the packet travels
on the WAN.
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