Zhone 6210 ユーザーガイド

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A. Terminology
A-2
 January 
2005
6210-A2-GB23-00
Your machine isn't really directly connected to the Internet, and it really has an 
internal local network address. When you provide the server's network address to 
others, you actually provide the address of the modem. The modem fakes the 
connection to your machine.
You should use the DMZ when you want to run a server that others will access 
from the Internet. Internal programs and servers (like print servers) should not be 
connected to the DMZ.
What is a Router?
The Internet is so large that a single network cannot handle all of the traffic and 
still deliver a reasonable level of service. To overcome this limitation, the network is 
broken down into smaller segments or subnets that can deliver good performance 
for the stations attached to that segment. This segmentation solves the problem of 
supporting a large number of stations, but introduces the problem of getting traffic 
from one subnet to another.
To accomplish this, devices called routers are placed between segments. If a 
machine wishes to contact another device on the same segment, it transmits to 
that station directly using a simple discovery technique. If the target station does 
not exist on the same segment as the source station, then the source actually has 
no idea how to get to the target.
One of the configuration parameters transmitted to each network device is its 
default gateway. This address is configured by the network administrators and it 
informs each personal computer or other network device where to send data if the 
target station does not reside on the same subnet as the source. If your machine 
can reach all stations on the same subnet (usually a building or a sector within a 
building), but cannot communicate outside of this area, it is usually because of an 
incorrectly configured default gateway.