I have this server setting: one web server with IPTABLES and a database server behind the web server.

The apache reponds requests for a while, then it doesn't repond to request from outside. I found that the TCP connection can be established by TELNET(so it appears IPTABLES is not guilty for this), but I can only input two characters and then the connection is terminated. There is no error_log and access_log. While I can access apache from the database server.

If I restart the apache server, it works for a while again.

Who knows what the problem could possibly be?