1
I have 3 computers in my network connected to the same router.
Computer A - my desktop computer Computer B - Web server Computer C - Mail server and SQL server
Everything is set up correctly externally which means I can telnet to IMAP port (143) on Computer C and Web server port (80) on Computer B.
But suddenly, in like a 10 minute interval or more often I cannot telnet to Computer C from the outside. I can telnet from Computer A and B. And I can telnet from Computer A to B from the outside.
I do not think the problem is the router. Computer C is new with Windows 2012 and I guess it is either a network problem, configuration etc on that computer. Do you have any more ideas of how to test this or?
Henrik
Posted 2013-06-29T07:48:51.080
Reputation: 131
2It is possible your ISP is blocking your mail server when it detects it. – Scott Goodgame – 2013-06-29T12:18:58.220
No, I have mail server on Server B. And it works with same ports. Thanks anyway! – Henrik – 2013-06-29T14:06:06.243
Got windows update recently? Some windows update may change your firewall rules... (on computer C). – Darius – 2013-06-29T16:07:35.010
Thanks for your feedback - found the reason - the switch got the same ip as the computer C. – Henrik – 2013-07-01T07:35:56.267