Hi, Just a quick update, I have gone through the tcpdump files from yesterday afternoon and overnight (server only, I haven't tried on the Windows clients yet).
Filtering on TCP RST <-- I have not found more that 2 or 3 instances for clients on the LAN. I'm still monitoring today so we'll see what comes out of that. I also had an epiphany yesterday evening which was that by default Ubuntu ( and I believe most mainstream distros do the same ) has IPv6 activated however I seem to remember reading somewhere ( can't remember where or when, that's old age for you! ;) ) that Windows didn't play that well with IPv6. To that end I have disabled IPv6 on the mail server, so far I haven't had any reported problems. That may be because they stopped bothering to tell me I suppose but I have prompted a couple of times and nobody has said anything. I'll keep you posted. On Thu, Jun 28, 2007 at 11:06:23AM +0100, Brian Candler wrote: >> TCP SYN --> >> TCP RST <-- >> >> Use tcpdump or wireshark (on client and/or server) if you wish to confirm >>or >> disprove this at the IP layer (*). Note that your switches will never >> generated TCP RST packets; only the end hosts participate in TCP. And hence >> if this is happening, it's nothing to do with your network infrastructure, >> and throwing money at your LAN won't help. > >Note, however, that firewalls intercept and participate in TCP. If there is >a [stateful or NAT] firewall between the affected clients and the server, it >could be causing the problem. For example, it could be reaching a configured >state table limit. > >This is another good reason to capture and analyse the problem properly. In >this case, capturing at both client and server sides, and comparing the >traces, would be useful. > >Regards, > >Brian. -- Regards, Adrian ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Courier-imap mailing list [email protected] Unsubscribe: https://lists.sourceforge.net/lists/listinfo/courier-imap
