User manual

EE400-R GigaFast Ethernet.
P 36
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4.4 Virtual Server
Generall
y
, NAT based routers/firewalls filter out all unreco
g
nized packets from the WAN to protect
y
our
Internal LAN computers; therefore, all LAN computers behind the EE400-R are invisible to the outside
Internet. However, some Internet servers (like WWW, FTP, E-mail) should be visible and accessible
by the outside Internet. As a result, the EE400-R provides Virtual Server functions to meet this demand. In
addition, the EE400-R also protects the servers and all other computers in the LAN simultaneousl
y
.
Since all the Internet servers always handle the fixed TCP/UDP service port number (like WWW is 80,
FTP is 21) any packets from the WAN which have a destination port number that matches a virtual
server’s port, then these packets will be forwarded to the pre-defined LAN’s IP. The destination
port number is also kept the same.