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10/100 hub for testing


I'm looking for a 10/100 Ethernet hub (or switch) I could lend for
testing, I'm having problems I think are hub problems. See below for
details. You are welcome to express ideas about what the problem might
be, too.

I ben op zoek naar een 10/100 Ethernet hub (of switch) voor testen. Ik
heb netwerk problemen, en ik denk dat ze van de hub stemmen. Als je
een idëe heb waarom ik dit probleem heb, zeg het.


Let me describe my setup first:

 Hardware / Ethernet:

 3Com 8 ports Ethernet 10/100 hub.

 On ports 5, 6 and 7 are computers, with NIC's. They all use
  dual-speed 10/100 NIC's, and operate at 100Mbps (light on hub

 On port 8 is an ADSL modem. It operates at 10Mbps (light on hub             
  orange). Connected through a crossed (in french "croisé", not              
  straight) cable. Hence, the uplink/normal button for port 8 is in          
  "normal" position. Serves Internet connection.

 Software / Network setup:

 One of the computer's serves as router for the other computers (it
  does masquerading (Source Network Address Translation)), and uses
  the ADSL modem through PPTP (point-to-point tunneling protocol),
  through the hub. Hence non-local network traffic goes from computer
  to router (through the hub), and from the router to the modem
  (through the hub again).

Problem description:

 This all has been working well for months, including some local
 traffic (ssh sessions from one computer to another), and fairly
 vanilla Internet traffic (HTTP, FTP, SMTP, POP3, etc
 traffic). Including quasi-daily transfer of some dozens of MB
 (megabytes) per FTP (typically about 60MB), at about 109 kB/s
 (kiloBYTES per second). (Yes, those are debian upgrades)

 Yesterday, I started listening to some Internet audio streaming
 (specifically, BBC streaming in OGG format). After 3 to 5 minutes,
 all Internet traffic suddenly stopped. I investigated, the modem
 wasn't answering to ping's. Computer-to-computer traffic was still

 After checking the router had no problem, I thought the modem had
 "crashed" and thus power-cycled it (turn it off, and then on
 again). Didn't help. I then went to see the hub. The 10M Collision
 LED was flashing constantly, with NO 10M network utilisation LED on
 or flashing. Power-cycling the hub resolved the problem.

 15 minutes later, same thing. I went to the hub, tried disconnecting
 all network connections, no effect (well, the "Collision LED goes
 off", but traffic still doesn't go to the modem). I tried putting the
 modem on another port. Didn't solve problem (yes, the port status LED
 went "up"). Power-cycling the hub again did the trick.

 7 minutes later, same thing. Power-cycled the hub, got really
 frustrated, stopped listening to the BBC.

Why do I think it is a hub problem?

 Because the only action that solves the problem is power-cycling the
 hub. Because it believes there are collisions when nothing is
 connected. Apparently, it enters some looping state where it blocks
 Ethernet traffic on the ports using 10Mbps.

What use pattern makes the problem appear?

 The only way I have found is listening to Internet streaming
 audio. In network terms, this would be a long, continuous, relatively
 low-bandwidth use: the stream is around 105kb/s (kiloBITs per
 second), and it goes trough the hub two times.

 Other uses that do not trigger the problem include a continuous 109
 kB/s (kiloBYTEs per second) stream for a short amount of time (a few
 minutes), that does go through the hub two times, too (FTP
 transfers). And various burst-uses (ssh sessions on the local
 network, typically an amount of data about one megabyte is pushed
 through the network at top speed every 30 seconds or so).

I don't own a hardware ethernet frame analyser to see exactly what
troubles the hub.

I'd like to check if the problem appears with another mixed 10/100


Als ik naar BBC OGG streaming luister, sluit mijn hub naar een paar
minuten mijn ADSL modem van mijn netwerk af, met het collisie lampje
voor 10M "blinking". De enige ding dat het weer goed maakt is de hele
hub van elektrische stroom af te sluiten en het stroom opnieuw naar de
hub te laten.

1 * 3COM hub 10/100, 8 connecties
3 * computers met 100 Mbps Ethernet. Een van die computers is een
    router (doet masquerading = source NAT)
1 * ADSL modem met 10 Mbps Ethernet

De router heeft een PPTP sessie over de hub met de ADSL modem.

De enige verschil ik zie met mijn vorige gebruik van het netwerk is:

 - Nu, circa 105 kb/s (kiloBIT per s) voor lange tijd
 - "Before", 109 kB/s (kiloBYTE per s) voor korte tijd voor internet,
   en heel korte "bursts" van meerderde MBps locaal (ssh sessies).


Thank you for your help,

Dank je voor jouw tijd,

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