Unstable Box

[m.saitoh@lac.co.jp]

Hello users:

 I'm suffering unexpected trouble which permitted packets can't
sometimes pass through  my Box, although nobody have never 
changed the rules nor configures.
The phenomenon is summarized the following,

1)  Sometimes, I can't telnet from inside-host to Internet-host.
2)  3 chains are related to this; FORWARD, PRE & POSTROUTING.
3)  This packet seems not to be dropped by Filtering rules.  
     Because all un-accepted packets are to be recorded in a log file.
4)  Packets come into Box, but go outside. (monitoring with tcpdump)
5)  Momory status looks well. (with vmstat)
6)  This problem recover automatically after 1 or few hours.
    To "reboot" the Box can be the way for recovery.

7)  Everywhen this phenomenon came out, my provider had problem &
    closed the connection to he Internet. However I'm not sure this
    is related to the phenomenon.

 I want to find out the reasons, what happened on my box.
How can I debug ?

Versions: iptables 1.1.1 & Linux 2.4.0-test8
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LAC Co., LTD.
Matsuhiko Saito