ELSA LANCOM Business 6000, Руководство пользователя

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Operating modes and functions
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ELSA LANCOM Business 6000
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EN
Please note that filters are not created in the event of an error in input nor are
error messages output. If you configure the filters manually, you should
always check that the desired filters have been created.
6.3.3 The hiding place—IP masquerading (NAT, PAT)
One of today's most common tasks for routers is connecting the numerous
workstation computers in a LAN to the network of all networks, the Internet.
Everyone should have the potential to access the WWW from his workstation
and be able to fetch bang up-to-date information for his work.
But this provokes objections from the network manager responsible for the
security of data on the company's network: Every workstation computer on
the Internet? Surely this means that anyone can get in from outside? —Not
true!
IP masquerading provides a hiding place for every computer while connected
with the Internet. Only the router module of the unit and its IP address are
visible on the Internet. The IP address can be fixed or assigned dynamically
by the provider. The computers in the LAN then use the router as a gateway
so that they themselves cannot be detected. To do this, the router separates
Internet and intranet, as if by a wall. Therefore, IP masquerading is also
called a “firewall function”. Another very effective firewall technology is the
targeted filtering of incoming data packets.
The use of IP masquerading is set individually for each route in the routing
table. The routing table can be found in the
ELSA LANconfig in the 'IP router'
configuration section on the 'Routing' tab, or in the
/Setup/IP-router-
module/IP-routing-table
menu.
6.4 Automatic IP address administration with DHCP
In order to operate smoothly in a TCP/IP network, all the devices in a local
network must have unique IP addresses.
They also need the addresses of DNS server and NBNS server as well as that
of a default gateway through which the data packets are to be routed from
addresses that are not available locally.
In a smaller network, it is still conceivable that these addresses could be
entered manually in all the computers in the network. In a larger network with
many workstation computers, however, this would simply be too enormous
of a task.