User's Manual

B222s User’s Guide 95
CHAPTER 10
Network Address Translation (NAT)
10.1 Overview
NAT ( Net work Address Translat ion - NAT, RFC 1631) is the t ranslation of t he I P address of a host in
a packet , for exam ple, t he source address of an out going packet , used within one net work t o a
different I P address known within anot her network.
10.1.1 What You Can Do in this Chapter
• Use the Port For w arding screen t o configure forward incom ing service request s to t he server( s)
on your local network (
Section 10.2 on page 96) .
• Use the DMZ screen t o vieiw and configure t he I P address of your net work DMZ. (
Section 10.3
on page 99
) .
• Use the Sessions screen to lim it the num ber of concurrent NAT sessions each client can use
( Sect ion 10.4 on page 99) .
10.1.2 What You Need To Know
The following term s and concept s m ay help as you read this chapt er.
Inside/Outside and Global/Local
I nside/ out side denot es where a host is located relat ive t o t he LTE Device, for exam ple, t he
com puters of your subscribers are the inside hosts, while t he web servers on the I nt ernet are the
out side host s.
Global/ local denot es the I P address of a host in a packet as t he packet traverses a r out er, for
exam ple, t he local address refers t o the I P address of a host when the packet is in t he local
network, while t he global address refers t o t he I P address of t he host w hen t he sam e packet is
traveling in t he WAN side.
NAT
I n t he sim plest form , NAT changes the sour ce I P address in a packet received from a subscriber
( t he inside local address) t o anot her ( the inside global address) before forwarding t he packet t o t he
WAN side. When t he response com es back, NAT t ranslat es the destinat ion address ( the inside
global addr ess) back t o t he inside local address before forwarding it t o the original inside host.