ZyXEL VMG4927-B50A User Guide - Page 169

NAT Definitions, What NAT Does

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Chapter 11 Network Address Translation (NAT) The following table describes the fields in this screen. Table 63 Network Setting > NAT > Sessions LABEL DESCRIPTION MAX NAT Session Per Host Use this field to set a limit to the number of concurrent NAT sessions each client host can have. If only a few clients use peer to peer applications, you can raise this number to improve their performance. With heavy peer-to-peer application use, lower this number to ensure no single client uses too many of the available NAT sessions. Apply Click this to save your changes on this screen. Cancel Click this to exit this screen without saving any changes. 11.9 Technical Reference This part contains more information regarding NAT. 11.9.1 NAT Definitions 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 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 that inside/outside refers to the location of a host, while global/local refers to the IP address of a host used in a packet. Thus, 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 64 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. NAT never changes the IP address (either local or global) of an outside host. 11.9.2 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. The global IP addresses for the inside hosts can be either static or dynamically assigned by the ISP. In addition, you can designate servers, for example, a web server and a telnet server, on your local VMG4927-B50A / VMG9827-B50A User's Guide 169

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Chapter 11 Network Address Translation (NAT)
VMG4927-B50A / VMG9827-B50A User’s Guide
169
The following table describes the fields in this screen.
11.9
Technical Reference
This part contains more information regarding NAT.
11.9.1
NAT Definitions
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 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 that inside/outside refers to the location of a host, while global/local refers to the IP address of a
host used in a packet. Thus, 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.
NAT never changes the IP address (either local or global) of an outside host.
11.9.2
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.
The global IP addresses for the inside hosts can be either static or dynamically assigned by the ISP. In
addition, you can designate servers, for example, a web server and a telnet server, on your local
Table 63
Network Setting > NAT > Sessions
LABEL
DESCRIPTION
MAX NAT
Session Per Host
Use this field to set a limit to the number of concurrent NAT sessions each client host can have.
If only a few clients use peer to peer applications, you can raise this number to improve their
performance. With heavy peer-to-peer application use, lower this number to ensure no single
client uses too many of the available NAT sessions.
Apply
Click this to save your changes on this screen.
Cancel
Click this to exit this screen without saving any changes.
Table 64
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.