prodtpd - kapcsolat szakad

Sziasztok,

kovetkezo erdekes problemam lenne, proftpd 2 kulonbozo gepen, kulonbozo halozatban, upload kozben teljesen random idokozonkent (max 10 perc) bontja a kapcsolatot, naha downloadnal is.
Mind1ik server-n Sarge fut, proftpd_1.2.10-11, iptables csomagszures van, PassivePorts 61000 61100 de nem hiszem hogy ez miatt csinalna.

Gepen levo net, stabil, nem szakadozik (1ik - enternet serverterem, 2ik - egyetemi serverterem )

gepek stabil gepek 2ik tobb mint 200 napja megy.

igazabol nincsen 5letem mi miatt csinalja, viszont igy hasznalhatatlanok, mivel ket gepen is hasonlo problema van, proftpd-re gyanakszom:

proftpd conf:
ServerName "xxxxx.hu"
ServerIdent on "Welcome to xxxxxx"
ServerType standalone
ServerAdmin xxxx@xxxxx.hu
DeferWelcome off

Port 21
Umask 002
TimeoutLogin 120
TimeoutIdle 600
TimeoutNoTransfer 900
TimeoutStalled 3600

User ftp
Group ftp

UseReverseDNS off

TransferLog /var/log/proftpd.trans
LogFormat default "%h %l %u %t \"%r\" %s %b"
LogFormat auth "%v[%P] %h %t \"%r\" %s"
LogFormat write "%h %l %u %t \"%r\" %s %b"

MaxClientsPerHost 2 "Maximum 2 kliens/host!"
MaxClients 10 "Maximum 10 kliens!"

<Global>
DisplayLogin welcome.msg
DisplayFirstChdir readme

AllowOverwrite yes
IdentlookUps off
ExtendedLog /var/log/proftpd.auth AUTH auth

DefaultRoot ~

</Global>

<Limit WRITE>
DenyAll
</Limit>

<VirtualHost ftp.xxxxx.hu>
ServerName "ftp.xxxx.hu"
ServerIdent on "xxxxx"
ServerAdmin xxxxx@xxxx.hu

AuthPAM off
SQLAuthTypes Backend
SQLAuthenticate users groups
SQLConnectInfo proftpd@localhost xxxxx xxxxxx
SQLUserInfo users userid passwd uid gid homedir shell
SQLGroupInfo groups groupid gid members

SQLLog PASS logincount
SQLNamedQuery logincount UPDATE "login_count=login_count+1 WHERE userid='%u'" users
SQLLog PASS lastlogin
SQLNamedQuery lastlogin UPDATE "last_login=now() WHERE userid='%u'" users
SQLLog RETR dlbytescount
SQLNamedQuery dlbytescount UPDATE "dl_bytes=dl_bytes+%b WHERE userid='%u'" users
SQLLog RETR dlcount
SQLNamedQuery dlcount UPDATE "dl_count=dl_count+1 WHERE userid='%u'" users
SQLLog STOR ulbytescount
SQLNamedQuery ulbytescount UPDATE "ul_bytes=ul_bytes+%b WHERE userid='%u'" users
SQLLog STOR ulcount
SQLNamedQuery ulcount UPDATE "ul_count=ul_count+1 WHERE userid='%u'" users

SQLUserWhereClause "disabled!=1 and (NOW()<=expires or expires=-1)"
RequireValidShell Off
PassivePorts 61000 61100

</VirtualHost>