Bug#647866: Network: Packages over hub via bnc not received
Thank you for your fast answer and support.
Please see my answers /remarks included below.
Ben Hutchings wrote ..
> On Mon, 2011-11-07 at 01:48 +0100, debian wrote:
> > Package: linux-base
> > Version: 2.6.32-38
> > Severity: normal
> > Hello,
> > sorry for this unspecific bug report / question:
> > After installing debian squeeze the networking does not work in the
> > following situation:
> > Situation:
> > I have a debian patched "Dockstar" (embedded system dockingstation NAS)
> > box which is connected to a hub.
> > This hub is connected via bnc-cable (coax) to another hub on which a
> > linux box (Suse) is connected (router to internet).
> > If Dockstar tries to connect to internet it "arps" for the gateway MAC
> > (arp-request is seen on all netork parts with wireshark).
> > The answer (arp-replay) is also seen an all network part.
> > The arp table on the dockstar will not be updated by this communication
> > ("arp -n" shows always "(incomplete)" for HWaddress) and continoues arp
> > request can be seen.
> > Any network packet directed to the dockstar can be seen on all parts of
> > the network (this were seen with whireshark) but in debian there is
> > nothing received.
> > If I connect the debian-dockstar and the linuxbox over the same hub
> > without bnc the communication is OK!
> > It seems NOT to be a hardware problem of the dockstar, because with
> > original firmware (also a linux) connection over bnc to internet works fine.
> > I found a information on internet about problem with older hub/network
> > hardware which inject some sort of incorrect crc errors
> > http://www.plugcomputer.org/plugforum/index.php?topic=5772.msg18770#msg18770
> > Is there a way to configure debian linux to ignore such crc errors?
> CRC checking is a hardware feature and should not be disabled. If you
> were to do so, you would find that the contents of the received packets
> are junk.
> I would guess that the problem is related to signal levels. Because you
> are using hubs, signals have to travel all the way from one computer to
> the other, whereas a switch or router will receive and re-transmit each
> packet. When you remove the coax cable you are shortening the distance
> between the computers and so the received signal is stronger and there
> are fewer errors.
So this could be tested with a short cable (but >0,5m) between two hubs.
I will try, but I do not think that this is the problem.
> Maybe the original firmware enables higher amplification for received
> signals, so the network interface can properly decode weak signals.
> What is the network driver and where is the source for the original
Following infos were catched from dockstar device.
With that version the network works well.
It seems to be debian also.
Pogoplug:~$ cat /proc/version
Linux version 126.96.36.199 (bdietrich@brad-ux) (gcc version 4.2.1) #57 Mon Aug 31 16:31:01 PDT 2009
Pogoplug:~$ uname -a
Linux Pogoplug 188.8.131.52 #57 Mon Aug 31 16:31:01 PDT 2009 armv5tejl unknown
Pogoplug:$ cat /proc/cpuinfo
Processor : ARM926EJ-S rev 1 (v5l)
BogoMIPS : 1192.75
Features : swp half thumb fastmult edsp
CPU implementer : 0x56
CPU architecture: 5TE
CPU variant : 0x2
CPU part : 0x131
CPU revision : 1
Cache type : write-back
Cache clean : cp15 c7 ops
Cache lockdown : format C
Cache format : Harvard
I size : 16384
I assoc : 4
I line length : 32
I sets : 128
D size : 16384
D assoc : 4
D line length : 32
D sets : 128
Hardware : Feroceon-KW
Revision : 0000
Serial : 0000000000000000
If you need more / other inforamtion please tell tell me.
> > What I do not understand is that all other linux boxes do not have this
> > problem.
> Because other people do not use 10BASE-2 and hubs!
That is not be the point.
I use this network for years with some linux and windows boxes.
There must be a difference between Suse and Debian squeeze.
If I use another linux computer in substitute for the dockstar at the same network point
the problem does not appear.
> > Is there a relevant change on kernel module concerning networking?
> Ben Hutchings
> You can't have everything. Where would you put it?