I have newly set up a proxy server for about 210 users. It runs ubuntu server 2012 and squid3. The problem is just after 1:30 am, if the users try to open google.com, youtube.com, facebook.com or wikipedia.org, connection times out. But at that time the server can ping those sites perfectly well. Even, if we telnet to the site and send GET, it dumps the HTML code in terminal. previously ubuntu desktop version was there and terminating network manager used to solve it for short period of time. So it seemed that network manager was interfering with other processes. But with server version no GUI network manager comes. So I am clueless about the problem. What can be the reason? How to fix it?
ok finally I guess I have fixed the problem. What it seems is there is something wrong with ipv6 addressing design with my isp, because in the specified time zone I cannot ping6 to google's ipv6 but ipv4 works perfectly. hence what I did is explicitly mentioned in squid.conf to prefer ipv4 and not ipv6. This seems to have fixed the problem. Thank you all fo your time. please see the following url for details http://stackoverflow.com/questions/12633884/squid3-cant-access-google-com-or-bing-com