ELSA LANCOM Business LC-4X00, Руководство пользователя

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Workshop
ELSA LANCOM Business
105
Internet access for all PCs on the LAN
The motivation
Many companies would like to have an Internet connection for all computers on their
local area network. Up to now there have been two reasons for arguing against this in
several instances:
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Having separate accounts with an Internet service provider (ISP) for each individual
computer or even buying IP addresses registered and valid on the Internet is, in most
cases, much too expensive. In addition there is the cost of setting up and
maintaining Internet access for each computer.
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A further worry is not knowing whether you are flinging wide the gates for access
onto the company's network from outside when you connect each individual
computer to the WWW.
The router solves both problems in a single function: IP masquerading. In short, this is
what happens:
The router is the only machine on the LAN to have a valid IP address on the Internet. This
can be allocated dynamically on dial-up by the Internet service provider using PPP for
instance (as with CompuServe etc). The network computers use addresses from a
protected range (addresses in the tens, for example). The entire local area network is
now ”hidden“ by IP masquerading behind the registered IP address of the router.
This process has even more benefits:
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IP masquerading makes Internet access simple.
Only one device needs to be configured. And the ELSA LANconfig setup wizards will
even help you do this.
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IP masquerading makes Internet access cost-effective.
All the computers on the local area network can use the IP address of the router to
the outside and so have access to the Internet. This means that many users will only
need a single account with the service provider. Furthermore, the router manages
the ISDN line automatically and only establishes a link to the service provider when
there is actually a need to transfer data.
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IP masquerading makes Internet access secure.
The computers in the local area network become invisible from outside. Only the IP
address of the router will be known on the Internet. It is therefore not possible to
access the local area network from outside; IP masquerading acts as an effective
firewall, separating Internet from Intranet. Besides, the router is the only interface
with the Internet, making it simpler to monitor than numerous individual workstation
machines.