Re: subnets & 2 NICS in a mashine
Robert Guthrie wrote:
> Okay, this I know about:
> On an ethernet network every packet of information that is transmitted by a
> computer is visible to all NICs on the network. For a NIC to actually accept
> a packet for it's machine, the packet must be addressed to that NIC's MAC
> address (the ethernet driver translates IPs to MACS when transmitting
> packets), or the nic must be in "promisquious mode", which allows it to
> accept all packets (special case used to sniff packets).
>
> It seems you think of packets traveling around on your network as if they
> were a road; the data hops in a car, pulls out of it's driveway, drives down
> the street and pulls into another driveway, then gets out and knocks on the
> door of the recipient.
Exactly what I assumed.
> A kind of wierd analogy might be like this: You're talking on a two-way
> radio (HAM, walkie-talkie, etc..), where only one person can talk at any
> given time. Each person is allowed 30 seconds maximum of talk time before
> they must pause and let someone else talk if they want. When someone starts
> tallking, they say "I want to talk to Fred." and then they start talking.
> Not being interrested in what is being told to fred, everyone else ignores
> what is being said until they hear the phrase "I want to talk to...".
>
> That's kind of what's going on on the physical side of the network (wire,
> NICs). Hope that helps your understanding.
I'm not to sure if this is a bit to simple.
What I had drawn out of some articles is:
When data is supposed to be sent to a certain computer and this
computer is not 'online' or wthin the subnet, the data would be
adressed to the gateway mashine and let this then decide what to do.
In case of the adressed mashine saying "here I am!" (because of being
in the same subnet) the data would be chopped in IP packets with each
packet containing a header with the IP-number or MAC number to be
adressed correctly. Otherwise - I guess - would the data be bounced
throughout the network and cause useless traffic?
Exactly this imagination makes me hard to understand why 2 NIC's on
one mashine need two subnets. I recently configurated the two cards in
the server to work within the same subnet which turned out that the
w95 client could not adress anything to the smb server on the
2-NIC-mashine.
Robert
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