On Thursday 13 January 2005 12:03 am, Eric A. Hicks wrote:
> SOTL wrote:
> >Switch
> >Non configurable
> >If an input package only goes to the port that contains the device that
> > the package is directed to. Can not figure this one out how the switch
> > knows to sent a package inputed to A to output B instead of C and what
> > happens if you need it to also go to D?
>
> My understanding of switches is that they maintain an internal database
> that logs things like <pseudo> "in port 1, I have a device with mac
> address xx:xx:xx:xx:xx:xx" </pseudo> So when your PC, plugged into
> port 2, wants to print to the printer in port 1, the switch goes "oh, I
> recognize the PC in port 1 with mac address blah, blah is sending data
> packets addressed to a device that I have in my database as being
> plugged into port 2, let me make a direct connection between those two
> ports to reduce traffic across the network. I think the reason they
> call them switches is because they work just like the old telephone
> operators did... they directly connect this phone to that one via a
> switching board. But the key to the whole technology is that they
> maintain an internal database.
>
> I have to agree with Paul's earlier comment about routers..... I think
> you are confusing firewalls with routers. All routers do is determine
> if packets should stay on the local subnetwork, or pass to a different,
> connected subnetwork. Like so...
>
> LAN A ------- Router -------- LAN B
>
> If a PC on LAN A is printing to a printer also on LAN A, then the
> packets hit the router... the router says "according to the packet
> destination (LAN A), I won't let this packet cross the router to LAN
> B" However, if that PC is sending an email with packets destined for
> an email server on LAN B, the packets hit the router and the router
> allows it to pass because the destination was not local.
>
> That was a very simplistic explanation, and I'm sure many people can
> shoot holes in what I explained above.... but essentially, routers just
> limit traffic. You don't want LAN traffic crossing the WAN. "Don't
> span the WAN" was the common saying when I studied this stuff.
>
> I'm pretty sure that what you were saying in your previous email was
> firewalling.. That's saying something like... all traffic that hits port
> 80 on the gateway, redirect that to 192.168.0.5:80. block all traffic
> on port 21 etc...
Thanks you are correct in that all of these devices are confusing to me with
the more explanation I read the less I understand.
If as you describe above you have 2 networks then the device limiting the
packets flow would to me be a firewall which is NOT what I have in mind.
I was assuming that both sides of your router were in the same network
something like
_________________
A --| |
B --| |
C --| Device |
D --| |
E --|_________________|
Where if the device was a router with A as a LAN input and B, C, D, E would be
outputs connected to various devices say a PC, PC, printer, and plotter and
if the device was programmable then one could direct exactly which packets
one wanted to which device. Your choice.
If on the other hand if the device was not programmable then it would be
either a switch with a built in table or a hub which sent all input packets
to all outputs. There being no effective difference between a hub and switch
at this level of adstraction. Of course, at a lower more basic lever there is
a great deal of difference.
As far as a bridge I have NO idea of what that device does. Best I can figure
out is that there is little difference between a switch and a bridge.
Am I finally getting the idea?
Thanks
Frank
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