Subject: server drops connection (ARP problem)

From: "Markus Koch" <[email-masked]>
Date: Fri, 16 Nov 2001 01:15:30 +0100

Hi

I have a severe problem and I just don't know what else to do. I can not
find any description of something similar on the internet.
Please read and help.

Following problem:
The server (now with Suse 7.2 / 2.4.4 iptables and ipchains disabled)
running netatalk and samba, suddenly without any appearent reason, drops all
network connections. When sniffing the net traffic from the server and
another linux box on the same network, it turns out, that the server does
not recognizes any packet on the net any more. The server sends ARP
questions, at first specificaly to certain computers it has been
comunicating with, and after he does not see any answer, he sends ARP
broadcasts. He never sees any answer. Sniffing the traffic from an other
linux box on the same segment, I can see that all computers answer the ARP
requests, they are on the wire, just not seen by the server. After different
amounts of time (5min to 10h) this condition suddenly dissappears. Suddenly
the server recognises the ARP answers and all is well again. Sometimes the
connection goes down like this when all clients are turned off and does not
come back up for the whole night until someone turns on the first client
(DHCP) computer in the net, then it comes back up. But more often it happens
during the day independently of how many clients (appletalk, samba and imap)
have connections to the server (these obviously time out). The outage
dissappears usually faster during the workday.
The other linux box with the same NIC and kernel (no server deamons
except bind and squid) pluged into the same HUB never shows these symtoms.

Here is what I have tied:
At first I tried the most obvious and changed the NIC. (from onboard
Etherexpress pro to realtek PCI card (the module for the onboard NIN is not
installed)).
Then I updated the Kernel and the whole system/deamons (including samba and
netatalk) from a 2.2.16-RAID (selfcompiled and patched) to the 7.2
distribution (Netatalk 1.4.99 (1.5) and Samba 2.2.0).
I tried out the suse standard 2.4.4 kernel, selfcompiled 2.4.4 and native
selfcompiled 2.4.7 with almost all kinds of network setting in the
kernelconfiguration.
Everything I have tried so far did not change the problem.

Harware:
Motherboard Asus P2B-LS 3xSCSI-HD and 1-SCSI-DAT  and  now Realtek PCI NIC
connected to a 10/100 Mbit noname HUB

Does anyone have an Idea?
What hardware should I change next.
Is there a way to realy debug what is going on in the NIC?
If nobody can help, a good mailinglist dealing with such problems would also
help.

Thanks

markus