ZyXEL Communications VMG1312-B Series, User Manual

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VMG1312-B Series User’s Guide
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C
H A P T E R
11
Network Address Translation (NAT)
11.1 Overview
This chapt er discusses how t o configure NAT on t he Device. NAT ( Net work Address Translat ion -
NAT, RFC 1631) is t he t ranslat ion 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 wit hin one net work t o a different I P address know n w it hin
anot her net work.
11.1.1 What You Can Do in this Chapter
• Use t he Por t For w a r din g screen t o configure forward incom ing service request s t o t he server( s)
on your local net work ( Sect ion 11.2 on page 186 ) .
• Use t he Applica t ion s screen t o forward incom ing service request s t o t he server( s) on your local
net work ( Sect ion 11.3 on page 189 ) .
• Use t he
Por t Tr igge r in g
screen t o add and configure t he Device’s t rigger port set t ings ( Sect ion
11.4 on page 190 ) .
• Use t he D M Z screen t o configure a default server ( Sect ion 11.5 on page 193 ) .
• Use t he ALG screen t o enable and disable t he NAT and SI P ( VoI P) ALG in t he Device ( Sect ion
11.6 on page 194 ) .
• Use t he Addr e ss M a pping screen t o configure t he Device's address m apping set t ings ( Sect ion
11.7 on page 194 ) .
11.1.2 What You Need To Know
Inside/Outside
I nside/ out side denot es where a host is locat ed relat ive t o t he Device, for exam ple, t he com put ers
of your subscribers are t he inside host s, while t he web servers on t he I nt ernet are t he out side
host s.
Global/Local
Global/ local denot es t he I P address of a host in a packet as t he packet t raverses a rout er, for
exam ple, t he local address refers t o t he I P address of a host when t he packet is in t he local
net work, while t he global address refers t o t he I P address of t he host when t he sam e packet is
t raveling in t he WAN side.
NAT
I n t he sim plest form , NAT changes t he source I P address in a packet received from a subscriber
( t he inside local address) t o anot her ( t he inside global address) before forwarding t he packet t o t he