D-Link DFL-1500 [69/271] Dfl 900 1500 user manual chapter 7 nat

DFL-900/1500 User Manual Chapter 7

NAT

Chapter 7

NAT

This chapter introduces NAT and explains how to implement it in DFL-1500.

To facilitate the explanation on how DFL-1500 implements NAT and how to use it, we zoom in the left part of

Figure 1-10

into

Figure 7-1.

7.1 Demands

1. The number of public IP address allocated to each Internet subscribers is often very limited compared to the number of PCs

in the LAN1. Additionally, public-IP hosts are directly exposed to the Internet and have more chances to be cracked by

intruders. As the

Figure 7-1 illustrated, you hope all the pcs located at LAN1 and DMZ1 can connect internet through

limited IP address (61.2.1.1).

Figure 7-1 All the internal PCs can connect internet through limited WAN IP address by using NAT technology

2. Internet servers provided by your company may open many ports by default that may be dangerous if exposed to the public

Internet. As the

Figure 7-2 illustrated, we make the real servers hide behind the DFL-1500. And all the internet clients can

still access the service of servers.