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anyone know who sell a old style Ethernet Hub?

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  anyone know who sell a old style Ethernet Hub? Todd <Todd@invalid.invalid> - 2014-10-03 19:20 -0700
    Re: anyone know who sell a old style Ethernet Hub? Richard Kettlewell <rjk@greenend.org.uk> - 2014-10-04 08:48 +0100
    Re: anyone know who sell a old style Ethernet Hub? Joe The Smoe <news@edrusb.is-a-geek.org> - 2014-10-04 10:33 +0200
      Re: anyone know who sell a old style Ethernet Hub? Mike Scott <usenet.16@scottsonline.org.uk.invalid> - 2014-10-04 17:19 +0100
      Re: anyone know who sell a old style Ethernet Hub? Marc Haber <mh+usenetspam1118@zugschl.us> - 2014-10-05 13:27 +0200
        Re: anyone know who sell a old style Ethernet Hub? Joe The Smoe <news@edrusb.is-a-geek.org> - 2014-10-05 21:07 +0200
          Re: anyone know who sell a old style Ethernet Hub? Marc Haber <mh+usenetspam1118@zugschl.us> - 2014-10-06 10:13 +0200
    Re: anyone know who sell a old style Ethernet Hub? Todd <Todd@invalid.invalid> - 2014-10-04 15:41 -0700
      Re: anyone know who sell a old style Ethernet Hub? Todd <Todd@invalid.invalid> - 2014-10-05 13:32 -0700
    Re: anyone know who sell a old style Ethernet Hub? Ant <ant@zimage.comANT> - 2014-10-05 00:45 -0700
    Re: anyone know who sell a old style Ethernet Hub? Kirk_Von_Rockstein <Kirk_Von_Rockstein@nowhere.invalid> - 2014-10-07 14:48 +0000

#3113 — anyone know who sell a old style Ethernet Hub?

Hi All,

I need to do some network monitoring with Wireshark.
(modbus/tcp).

I need an old fashioned hub (not a switch) to
put between an appliance and a pump so I can see
what is actually happening.

Problem: all I can find are switches.  Those
don't work with Wireshark.

Anyone know of a real hub out there.  Only need three
ports, but am not picky about more than that.

Prefer 100 Base-T, but can live with 10-base-T

Many thanks,
-T

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#3115

Todd <Todd@invalid.invalid> writes:
> I need to do some network monitoring with Wireshark.
> (modbus/tcp).
>
> I need an old fashioned hub (not a switch) to
> put between an appliance and a pump so I can see
> what is actually happening.
>
> Problem: all I can find are switches.  Those
> don't work with Wireshark.
>
> Anyone know of a real hub out there.  Only need three
> ports, but am not picky about more than that.
>
> Prefer 100 Base-T, but can live with 10-base-T

No idea.  If you can’t find one, if you have a Linux box with at least
two ethernet ports you should be able to bridge them together, put it
between your two endpoints, and monitor the traffic on that.

-- 
http://www.greenend.org.uk/rjk/

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#3116

On 04/10/2014 04:20, Todd wrote:
> Hi All,
> 
> I need to do some network monitoring with Wireshark.
> (modbus/tcp).
> 
> I need an old fashioned hub (not a switch) to
> put between an appliance and a pump so I can see
> what is actually happening.
> 
> Problem: all I can find are switches.  Those
> don't work with Wireshark.

You can use a switch that has port mirroring feature.

> 
> Anyone know of a real hub out there.  Only need three
> ports, but am not picky about more than that.

Be careful about duplex setting when using a hub (always half duplex)!
If you have forced full duplex on one (or more) host(s), collisions will
occur and will not be noticed by anyone, no retransmission will occur
and packets that collided will be dropped silently because of at least a
wrong CRC.

> 
> Prefer 100 Base-T, but can live with 10-base-T
> 
> Many thanks,
> -T

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#3118

On 04/10/14 09:33, Joe The Smoe wrote:
> On 04/10/2014 04:20, Todd wrote:
>> Hi All,
>>
>> I need to do some network monitoring with Wireshark.
>> (modbus/tcp).
>>
>> I need an old fashioned hub (not a switch) to
>> put between an appliance and a pump so I can see
>> what is actually happening.
>>
>> Problem: all I can find are switches.  Those
>> don't work with Wireshark.
>
> You can use a switch that has port mirroring feature.
>
>>
>> Anyone know of a real hub out there.  Only need three
>> ports, but am not picky about more than that.
>
> Be careful about duplex setting when using a hub (always half duplex)!
> If you have forced full duplex on one (or more) host(s), collisions will
> occur and will not be noticed by anyone, no retransmission will occur
> and packets that collided will be dropped silently because of at least a
> wrong CRC.

? Not a problem I ever experienced.

How about
http://www.amazon.co.uk/D-Link-DE-805TP-5-port-Ethernet-10Mbps/dp/B0000687B5

by the way?


>
>>
>> Prefer 100 Base-T, but can live with 10-base-T
>>
>> Many thanks,
>> -T
>


-- 
Mike Scott (unet2 <at> [deletethis] scottsonline.org.uk)
Harlow Essex England

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#3123

Joe The Smoe <news@edrusb.is-a-geek.org> wrote:
>Be careful about duplex setting when using a hub (always half duplex)!
>If you have forced full duplex on one (or more) host(s), collisions will
>occur and will not be noticed by anyone,

Until here, things are marginnally ok. People will of course notice
abysmally bad performance.

>no retransmission will occur
>and packets that collided will be dropped silently because of at least a
>wrong CRC.

This is bullshit. TCP will notice packet loss and retransmit. UDP
won't.

Greetings
Marc
-- 
-------------------------------------- !! No courtesy copies, please !! -----
Marc Haber         |   " Questions are the         | Mailadresse im Header
Mannheim, Germany  |     Beginning of Wisdom "     | http://www.zugschlus.de/
Nordisch by Nature | Lt. Worf, TNG "Rightful Heir" | Fon: *49 621 72739834

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#3126

On 05/10/2014 13:27, Marc Haber wrote:
> Joe The Smoe <news@edrusb.is-a-geek.org> wrote:
>> Be careful about duplex setting when using a hub (always half duplex)!
>> If you have forced full duplex on one (or more) host(s), collisions will
>> occur and will not be noticed by anyone,
> 
> Until here, things are marginnally ok. People will of course notice
> abysmally bad performance.
> 
>> no retransmission will occur
>> and packets that collided will be dropped silently because of at least a
>> wrong CRC.
> 
> This is bullshit.

not that much,

>
>TCP will notice packet loss and retransmit. UDP
> won't.

a hub does not work at layer 4 like TCP or UDP does. I didn't assume
anything about layer 3 (IP, IPX, OSI, etc.) nor upper layers... So let
me be clearer:

If two hosts forced in full duplex are connected to a hub, and send each
an Ethernet Frame at the same time, none of them will be able to read
the frame sent by the other host (layer 2 CRC error, runt, alignment
error, etc.) nor they will be able to notice that their own frame
collided. So the frames are lost, both.

If they were in half duplex, they would neither be able to read the
other host's frame, but would have seen the collision and would have
retransmitted their own frame after an exponential backoff time. This
has nothing related to TCP, we stay at layer 2 here.

Of course if at layer 4 TCP is used, the lost frame will be noticed. And
if UDP is used, the packet loss may also be noticed depending on the
application used on top (TFTP for example will handle such packet loss,
NTP also while it does not care/need retransmission, but can suffer some
packet loss).

The difference is the time it will take for a packet loss to be
retransmitted. At layer 2 this is a matter of milliseconds while at
layer 4 (TCP for example) this is a matter of seconds.

The consequences for the user is the impression of a very slow or quite
unusable network.

> 
> Greetings
> Marc

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#3128

Joe The Smoe <news@edrusb.is-a-geek.org> wrote:
>If two hosts forced in full duplex are connected to a hub, and send each
>an Ethernet Frame at the same time, none of them will be able to read
>the frame sent by the other host (layer 2 CRC error, runt, alignment
>error, etc.) nor they will be able to notice that their own frame
>collided. So the frames are lost, both.

Yes. Full Duplex basically means that collection detection is turned
off. This - on a xBaseT-Link which has separate wires for transmit and
receive - works only if there are only two devices on the link. Hence,
a switch.

>Of course if at layer 4 TCP is used, the lost frame will be noticed. And
>if UDP is used, the packet loss may also be noticed depending on the
>application used on top (TFTP for example will handle such packet loss,
>NTP also while it does not care/need retransmission, but can suffer some
>packet loss).

And both TCP or UDP based streaming services will be dead in the
water, with UDP handling the situation much better.

This is the practical result. Users usually don't care about ethernet
frames, they care about IP packets, TCP streams and UDP datagrams.

>The difference is the time it will take for a packet loss to be
>retransmitted. At layer 2 this is a matter of milliseconds while at
>layer 4 (TCP for example) this is a matter of seconds.

Agreed.

>The consequences for the user is the impression of a very slow or quite
>unusable network.

Agreed. This has become more critical in times of IP telephony.

Greetings
Marc
-- 
-------------------------------------- !! No courtesy copies, please !! -----
Marc Haber         |   " Questions are the         | Mailadresse im Header
Mannheim, Germany  |     Beginning of Wisdom "     | http://www.zugschlus.de/
Nordisch by Nature | Lt. Worf, TNG "Rightful Heir" | Fon: *49 621 72739834

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#3121

On 10/03/2014 07:20 PM, Todd wrote:
> Hi All,
>
> I need to do some network monitoring with Wireshark.
> (modbus/tcp).
>
> I need an old fashioned hub (not a switch) to
> put between an appliance and a pump so I can see
> what is actually happening.
>
> Problem: all I can find are switches.  Those
> don't work with Wireshark.
>
> Anyone know of a real hub out there.  Only need three
> ports, but am not picky about more than that.
>
> Prefer 100 Base-T, but can live with 10-base-T
>
> Many thanks,
> -T

Found on in my junk box.  yippee!

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#3127

On 10/04/2014 03:41 PM, Todd wrote:
> On 10/03/2014 07:20 PM, Todd wrote:
>> Hi All,
>>
>> I need to do some network monitoring with Wireshark.
>> (modbus/tcp).
>>
>> I need an old fashioned hub (not a switch) to
>> put between an appliance and a pump so I can see
>> what is actually happening.
>>
>> Problem: all I can find are switches.  Those
>> don't work with Wireshark.
>>
>> Anyone know of a real hub out there.  Only need three
>> ports, but am not picky about more than that.
>>
>> Prefer 100 Base-T, but can live with 10-base-T
>>
>> Many thanks,
>> -T
>
> Found on in my junk box.  yippee!
>

"on" should be "one"

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
the riddle wrapped in an enigma wrapped
in a couple slices of baloney
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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#3122

Craig's List, eBay, etc.? I got rid of my Netgear hub years ago since it 
sucked compared to switches.


On 10/3/2014 7:20 PM PT, Todd typed:

> Hi All,
>
> I need to do some network monitoring with Wireshark.
> (modbus/tcp).
>
> I need an old fashioned hub (not a switch) to
> put between an appliance and a pump so I can see
> what is actually happening.
>
> Problem: all I can find are switches.  Those
> don't work with Wireshark.
>
> Anyone know of a real hub out there.  Only need three
> ports, but am not picky about more than that.
>
> Prefer 100 Base-T, but can live with 10-base-T
>
> Many thanks,
> -T
-- 
"I go out of my way to avoid stepping on ants." --Terry McGovern, 
daughter of Senator George and Eleanor McGovern, subject of the book 
"Terry by her father"
    /\___/\         Ant(Dude) @ http://antfarm.ma.cx (Personal Web Site)
   / /\ /\ \                Ant's Quality Foraged Links: http://aqfl.net
  | |o   o| |
     \ _ /        If crediting, then use Ant nickname and AQFL URL/link.
      ( )         If e-mailing, then axe ANT from its address if needed.
Ant is currently not listening to any songs on this computer.

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#3131

On 2014-10-04, Todd <Todd@invalid.invalid> wrote:
> Hi All,
>
> I need to do some network monitoring with Wireshark.
> (modbus/tcp).
>
> I need an old fashioned hub (not a switch) to
> put between an appliance and a pump so I can see
> what is actually happening.
>
> Problem: all I can find are switches.  Those
> don't work with Wireshark.
>
> Anyone know of a real hub out there.  Only need three
> ports, but am not picky about more than that.
>
> Prefer 100 Base-T, but can live with 10-base-T
>
> Many thanks,
> -T

Posting this for reference should someone search for similar
in the future.

Hub Reference
http://wiki.wireshark.org/HubReference

List of Switches with port mirroring
http://www.miarec.com/knowledge/switches-port-mirroring
http://wiki.wireshark.org/SwitchReference

Tap Reference
http://wiki.wireshark.org/TapReference

More Good Info
http://wiki.wireshark.org/FrontPage

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