Re: tcpdump broken after rh9 2.4.20-27.9 kernel upgrade

From: Robert Brown (eli_at_typhoon.xnet.com)
Date: 12/28/03

  • Next message: Robert Brown: "Re: tcpdump broken?" 
    To: redhat-list@redhat.com
Date: Sun, 28 Dec 2003 09:37:30 -0600 (CST)

    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 

    -- 
--------  "And there came a writing to him from Elijah"  [2Ch 21:12]  --------
R. J. Brown III  rj@elilabs.com http://www.elilabs.com/~rj  voice 859 567-7311
Elijah Laboratories Inc.    P. O. Box 166, Warsaw KY 41095    fax 859 567-7311
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  • Next message: Robert Brown: "Re: tcpdump broken?"

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