lge fiber-optic loose connection for 1-6s

Paul Bielecki pawciobiel at gmail.com
Tue Jun 5 17:28:33 UTC 2007

Hello All

I have network connection problems with my small database/samba server.
Machine is on small shuttle box with lge fiber-optic 1000baseSX on LAN
and rl0 to VPN connection.
Server been set up by somebody else, about 4 years ago and have not
been update since.
I have 6x FreeBSD +2x linux + 4x M$ servers, but it is only one server
I have connection problems with.

It is FreeBSD 4.8 stable, Mysql 4.0.12, Samba 2.2.8

Network: 330 machines + network printers; 60 machines including this
server on, printers are on and the rest lan is,,
Default gateway is set to host in
rl link is connected to a second FreeBSD box which act only as a VPN,
There is one main switch which connects servers and uplinks from all
rooms and buildings.
Almost all windows machines in network are up-to date and all have
anti virus software installed.

What happen is that occasionally, from 6 to 20 times a day, all
machines seems to lose connection with this server for 1-6 seconds.

If it happens
-I can ping google.com or other host in the same network from server
itself and I have reply (?)
-I lose my ssh connection to this server
-there is no errors or warnings in messages apart smbd errors
-samba gives me lots of "smbd read_data: read failure for 4. Error =
Operation time out" or smbd_oplock/oplock break.
-tcpdump shows lots of ACK packtes from to server on 139

I think that having and as a one big thing
doesn't help, believe that it should be set up with  VLANs but I can't
change it just like that.
The second thing is that M$ network is not configured properly, there
should be one wins server or PDC, no bcasts.

I use to just blindly watch tcpdump -v -s 255 -i lge0 port not 22 and
port not 139 and not icmp
but I dont know what should I look for.

Let me know your thoughts and please give me some "tips" how can I
diagnose what can cause my problems.

some help with tcpdump would be much appreciated too,
for instance:
17:05:49.644256 0.00:01:e6:9d:07:16.452 >
0.ff:ff:ff:ff:ff:ff.452:ipx-sap-resp 30c '0001E69D071680DDNPI9D0716'
addr 0.00:01:e6:9d:07:16
17:33:04.521449 802.1d config 8000.00:05:5d:1f:00:80.8002 root
8000.00:05:5d:1f:00:80 pathcost 0 age 0 max 20 hello 2 fdelay 15

# printers
17:33:07.370377 > HP-DEVICE-DISC.MCAST.NET.svrloc:
[udp sum ok] udp 151 (ttl 4, id 51568, len 179)
17:05:18.409507 >
[udp sum ok] NBT UDP PACKET(138) (ttl 60, id 14452, len 229)
17:05:18.757053 >
[udp sum ok] NBT UDP PACKET(138) (ttl 60, id 20727, len 229)

# another samba server to bcast
17:05:29.708120 > [udp sum ok]
NBT UDP PACKET(137): QUERY; REQUEST; BROADCAST (DF) (ttl 64, id 0, len

Thanks in advance

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