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Chapter 6:
Understanding Network Hardware
Routers must be programmed to function correctly. They need to have the addresses
assigned to each of their ports, and various network protocol settings must be configured.
Routers are usually programmed in one of two ways:
Most routers include an RS-232C port. You can connect a terminal or PC with
terminal emulation software to this port and program the router in text mode.
Most routers have network-based software that enables you to program the
router, often using graphical tools or a simple web interface.
The method you use depends on the router and your security needs. (You might
want to disable network-based router programming so that unauthorized users cannot
change the router's configuration.) Figure 64 shows an example of a network that uses
routers.
Gateways
Gateways are application-specific interfaces that link all seven layers of the OSI model
when they are dissimilar at any or all levels. For instance, if you need to connect a
network that uses one of the OSI networking models to one using IBM's Systems
Network Architecture (SNA) model, use a gateway. Gateways can also translate from
Ethernet to Token Ring, although simpler solutions than gateways exist if you need
such a translation. Because gateways must translate so much, they tend to be slower
than other solutions, particularly under heavy loads.
The primary use for gateways today is for handling e-mail. POP3 and SMTP are
two examples of protocols that are handled by gateways. Most e-mail systems that can
connect to disparate systems either use a computer set up as a gateway for that chore
or let the e-mail server handle the gateway chores itself.
Figure 6-4.
A network using routers
Summary :
For instance, if you need to connect a network that uses one of the OSI networking models to one using IBM's Systems Network Architecture (SNA) model, use a gateway. Most e-mail systems that can connect to disparate systems either use a computer set up as a gateway for that chore or let the e-mail server handle the gateway chores itself.
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