3Com OfficeConnect 3C16771 User Manual page 147

Increasing the number of IP addresses available using NAT
172.20.54.212
Internet. The remaining PCs are the workstations.
All IP addresses are statically configured on the PCs. The
ISP's Internet Router has an IP address of
and there is a DNS server at
only six IP addresses are actually received by the PCs, so you
can assign a seventh IP address to the Internet Firewall
DMZ. Keep the remaining ones in reserve for the addition
of further equipment to the network.
In this example, assign a web address of
to the Internet Firewall DMZ, because this is in the valid
range provided by the ISP, and is not used by the servers, or
any other PC that needs to be visible on the Internet.
This example shows the servers using the DMZ port on the
Internet Firewall DMZ, so that the servers are accessible
from the Internet, but are protected from attacks. The
server access can be logged and monitored. All the other
PCs are on the LAN port, and so cannot be accessed from
the Internet, unless you specifically enable this. There are
no special Internet access requirements, such as blocking
IRC or NNTP.
1 Switch off the cable modem and connect the WAN and
LAN ports.
a Connect the WAN port to the Ethernet port on the cable
modem.
b Connect the LAN port to the hub or switch that all the
PCs (except the servers) are connected together
through, or directly to one PC that you use for
managing the Internet Firewall DMZ.
Connecting the Internet Firewall directly to one PC reduces
the risk of someone else on the network configuring
Internet Firewall before you have changed the default
password.
c Make sure that the servers are connected to the DMZ
port through a separate hub or switch. Using the same
hub or switch that is being used on the LAN port will
bypass the firewall security.
to
172.20.54.214
172.20.54.253
must be visible on the
172.20.54.1
. In this case,
172.20.54.217
147
,