MessageIf by non-switched 10/100 hub you mean one that does not have
a two port switch built into it that separates the 10mbit hub from the
100mbit hub and where the ports
are autosensing (to determine to which of the two hubs inside the box the
port should be wired to)
then I am pretty sure that such a hub does not and can not exist.
The network link speed is a physical layer property for the
collission-domain and as such it must be identical
for all stations connected to the same physical layer.
Thus it is impossible with ethernet to connect stations with different link
speeds such as 10mbit and 100mbit
stations on the same collission domain since the physical layers would be
incompatible and can not interoperate.
To do this a device must terminate the physical layers and keep the two
different collission-domains separated
since they are not compatible on the physical layer.
Commonly this is done by implementing two separate hubs inside the same
enclosure, one hub that only
works with a 10mbit physical layer and one other hub that only works with
the 100mbit physical layer.
The ports themself can autodetect which speed setting the attached station
is using and can rewire itself to connect to
that hub (of the two hubs inside the box) that has the compatible physical
layer.
In order to connect the two hubs internally to eachothers the devices
usually implements a 2 port switch that is implemented completely inside the
enclosure and connects with one port to the 10mbit physical layer and the
other port to the 100mbit physical layer.
This works since this device is a switch and thus a layer 2 device. Since
it is a layer two device it terminates the physical layer on each side of
the switch and conencts both hubs into one single larger broadcast-domain.
You will still have two separate physical collission-domains and as usual
one can not sniff packets outside of the
collission-domain where the sniffer is attached.
The reason for those types of devices is that historically switches have
bene expensive and hubs have been
cheap and thus allowed two hubs + a 2-port switch being cheaper to produce
than a single multi-port switch.
It would create a sort of multi speed hub that were cheaper than a switch.
Today there is no reason to use switched-hubs anymore since the pricing for
unmanaged switches with few ports have fallen so much that there is no price
difference.
But an unmanaged switch would still not help you since those would terminate
the physical layer at each port (as a switch does) and still prevent
sniffing since it is not possible to capture packets outside of the
collission domain and you sniffer would only share the same broadcast domain
(but not collission domain) as the hosts you want to sniff.
I think your only options are either to get a managed switch and run it in
spanning/mirroring mode or to get an active/passive inline tap.
----- Original Message -----
From: J T
To: 'ethereal-users@xxxxxxxxxxxx'
Sent: Thursday, June 26, 2003 10:58 PM
Subject: [Ethereal-users] Looking for a new non-switched hub
Hi all - I'm doing some sniffs on my network and need to find a non-switched
10/100 hub (preferably non-auto sensing as well to eliminate any 'smarts'
from the device) - Any suggestions?
Jeffrey Threlfall
Sr. Network Administrator
Healthcare Automation
VOX - 401.691.3240
Email - JT@xxxxxxxxxxxxxxxxxxxxxxxxx
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