Wireless/Redundant Edge Services xl Module Management and Configuration Guide WS.02.xx and greater

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Introduction
ProCurve Wireless Edge Services xl Module
■ Static source NAT with optional port translation—The module
translates a single source IP address to a single new address.
Typically, the address after translation is an IP address that is assigned
to the Wireless Edge Services xl Module. However, you can use a
different IP address as long as it is not assigned to another device. If you
choose not to use one of the module’s IP addresses, you must configure
proxy ARP so that the module can respond to ARP requests for the
NATed IP address.
You can optionally configure the module to translate the packet’s source
port to a new port.
■ Static destination NAT with port forwarding and optional port
translation—The module translates packets destined to a specific IP
address (typically one of the module’s own) to a new IP address. It then
forwards the traffic toward the new destination.
Port forwarding allows the module to differentiate between traffic sent to
the same IP address but different ports. For example, port forwarding can
translate a packet sent to its public IP address on the HTTP port (80) to
one IP address but translate a packet sent to the FTP port (21) to a
different address. Port forwarding allows multiple servers to share the
same public IP address.
Port translation, an additional option, allows the Wireless Edge Services
xl Module to translate the destination port as well as the destination IP
address. For example, the module can receive an HTTP packet on port 80
and change its destination to a Web server that uses the private port 55000.
You can learn more about these capabilities, including how to enable them, in
Chapter 8: Configuring Network Address Translation (NAT). The section
below gives some examples of when to use NAT.
Uses for NAT. Typically, NAT works at the interface between two networks
controlled by separate entities. For example, you are probably familiar with
how NAT functions on the Internet. The NAT device sits between your private
network and the Internet. It intercepts packets sent from the private network
to the Internet, changing all private source addresses to a single public IP
address that is known on the Internet. If hosts on the Internet need to access
a device in your private network, such as a Web server, the NAT device
performs destination NAT in the other direction, translating traffic destined
for the publicly known IP address to the correct private IP address.