What You Can Do; What You Need To Know - ZyXEL Communications NBG-418N v2 User Manual

10.2 What You Can Do

• Use the General screen to enable NAT and set a default server
• Use the Application screen to change your NBG-418N v2's port forwarding settings
10.4 on page

10.2.1 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 NBG-418N v2, 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.
Table 42 NAT Definitions
ITEM
Inside
Outside
Local
Global
Note: NAT never changes the IP address (either local or global) of an outside host.
What NAT Does
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. Note
that the IP address (either local or global) of an outside host is never changed.
Chapter 10 Network Address Translation
103).
DESCRIPTION
This refers to the host on the LAN.
This refers to the host on the WAN.
This refers to the packet address (source or destination) as the packet travels on the LAN.
This refers to the packet address (source or destination) as the packet travels on the WAN.
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(Section 10.3 on page 102).
(Section