[Wolves] Silly question but...

[chris procter]

> Ok, this may seem like a silly question to most of
> you, but I don't
> know.  So, what is the difference between a router,
> a broadband router
> and router with an ADSL modem on board.

A router routes information sent to it across the
network by IP address.

A router has several network interfaces each connected
to a different network (one to your home LAN, and one
to the phone companies network say). When it receives
a packet of data it looks at the headers to determine
which IP address its being sent to and then consults a
table stored in memory as to which network interface
to pass the packet on on (so if it sees the packet is
destined for you desktop machines IP it passes it out
on the LAN interface, if its for slashdot it passes it
out on the external interface)

Routers are switches, but whereas an ethernet switch
routes packets depending on their MAC address (which
is hardwired into your network card), routers route by
IP address which is not hardware dependant. This means
that they can actually use a different protocols on
different interfaces, so a broadband router will have
one interface that speaks ethernet (a standard network
connection) and one that speaks broadband of some sort
(say ADSL or ISDN).

Many routers allow you to change their network
interface hardware so you can take out an ethernet
card and put in a ISDN card and turn it into an ISDN
router. This has no effect on the router itself
because its doing all its routing by IP.

Routers were explained to me once as being telephone
exchanges for IP traffic. Its not really true but its
not a bad idea to start from.

chris


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