ZyXEL NBG5615 User Guide - Page 139
NAT, 15.1 Overview, 15.1.1 What You Can Do, What You Can
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CHAPTER 15 NAT 15.1 Overview NAT (Network Address Translation - NAT, RFC 1631) is the translation of the IP address of a host in a packet. For example, the source address of an outgoing packet, used within one network is changed to a different IP address known within another network. The figure below is a simple illustration of a NAT network. You want to assign ports 21-25 to one FTP, Telnet and SMTP server (A in the example), port 80 to another (B in the example) and assign a default server IP address of 192.168.1.35 to a third (C in the example). You assign the LAN IP addresses to the devices (A to D) connected to your NBG5615. The ISP assigns the WAN IP address. The NAT network appears as a single host on the Internet. All traffic coming from A to D going out to the Internet use the IP address of the NBG5615, which is 192.168.1.1. Figure 81 NAT Example A: 192.168.1.33 FTP, Telnet, SNMP Ports 21 to 25 LAN WAN B: 192.168.1.34 Port 80 192.168.1.1 C: 192.168.1.35 IP address assigned by ISP This chapter discusses how to configure NAT on the NBG5615. Note: You must create a firewall rule in addition to setting up NAT, to allow traffic from the WAN to be forwarded through the NBG5615. 15.1.1 What You Can Do • Use the General screen to enable NAT (Section 15.2 on page 141). NBG5615 User's Guide 139