[plug] OT: 10/100 hubs

[Matt Kemner]

On Tue, 10 Apr 2001, Kevin Shackleton wrote:

> I recently bought a DLink 8-port 10/100 "switching hub" for about $360,
> came with 4 network cards too (though some would complain that they're
> only Realtek 8139's).  Seems pretty good though I can't confirm that it
> really "switches" properly.

Was it a "10/100 switch" or a "Fast Ethernet switch"?

You have to be careful these days, because a 10/100 switch is where it is
really 2 seperate hubs - one running the 10Mb network, and one running the
100Mb network, joined by a bridge - so it's not a real "switch" because
you will still get shared traffic - eg if you have 4 machines at 100Mb you
will get a total of 100Mb of bandwidth shared by all machines.

The easiest way to find out if you really have a switch, and you have at
least 3 machines connected to the hub of which at least one is Linux[1]
is to run tcpdump on the Linux machine and then ping the 2nd machine from
the 3rd machine. If you have a switch you should see nothing. If you can
see the ping packets on tcpdump you have a hub.

 - Matt
[1] Of course any OS with a packet sniffer will do