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Re: tcpdump broken after rh9 2.4.20-27.9 kernel upgrade



Harry Hoffman writes:
 > Robert,
 > 
 > Glad to hear it's working again :-)
 > 
 > Have you considered reasearching "true" 100bt hubs (ie-> something from hp or
 > cisco) and then searching for it on ebay? It may turn out to be your best bet as
 > there is still alot of older equip. on ebay that would probably meet your needs
 > in terms of the hub only.

Well, I haven't condemmed the hubs just yet.  Before I bought them, I
contacted the manufacturer via their tech support phone line, and I
verified that the units I was interested in were indeed true hubs, and 
not switches.  I specifically asked if every packet transmitted thru
the hub would appear on every port of that hub, and they answered
yes.  They also make a 10/100baseT switch for about the same price, so 
I assume they understand the difference.  

If I can't work this out by tomorow, I will give them another call.
If it turns out that these devices are not really hubs after all, then 
I am going to be really upset!

I suspect that these are intelligent store-and-forward units that are
almost the same as switches, operating as follows:

1.  A packet is sent to the device.

2.  The device reads the packet into a holding buffer.

3.  The device sends the buffer contents to all other ports.

Now with this logic, each port could be operating in any of the 4
modes of full-10, full-100, half-10, or half-100, since the input and
output are buffered.  

Note that if the device examines the MAC address in the incoming
packet, then if it only sends it to a port it has received packets
from previously with that same MAC address as source, then you have a
switch instead of a hub.  I expect that the hub and the switch are
identical devices, differentiated only by a firmware option, or
perhaps a jumper internally.

Incidently, the hubs I am using are Linksys EFAH08W units, as shown
here:

   http://www.linksys.com/products/product.asp?grid=34&scid=31&prid=54

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