TMS zl Management and Configuration Guide ST.1.1.100226

5-2

Network Address Translation

Overview

Network Address Translation (NAT) is the process of translating network IP

addresses in a way that is transparent to the end users. It has traditionally been

a method of translating internal, private IP addresses into public IP addresses.

Companies typically choose to translate internal IP addresses for address

conservation.

NAT can be used to conserve IP addresses by having all internal devices use

the external IP address assigned to a NAT device when they request a connec-

tion to the external network. Alternatively, a small pool of addresses can be

reserved for use outside the network. When an internal device requests a

connection to the external network, it is assigned one of those addresses.

When the session ends, the IP address is returned to the pool for use by the

next device that requests a connection. This is a viable way to address today’s

IP address shortage as well as network growth.

The TMS zl Module can be deployed on the network perimeter to perform

traditional NAT functions. However, as companies have adapted their net-

works to meet the ever-changing face of business, the boundaries between

private and public networks have blurred. The Internet has become a critical

work tool for nearly every company, and companies have opened parts of their

private network to guests—such as partners and customers—allowing tem-

porary and permanent accounts with varying levels of access.

As a result of this expanding network, companies may also want to translate

addresses within their networks. The TMS zl Module can be used for this

purpose. For example, your company adds a computer lab for guests. Rather

than assign the guests IP addresses on internal VLANs or extend a guest VLAN

throughout the entire private network, you could have the TMS zl Module

perform NAT on traffic between the guest network and the rest of the internal

network.

On the TMS zl Module, NAT is configurable per zone, per VLAN, per IP range,

or even per IP address.