This is my case. We have a SIP telephony system based on OpenSER with a redundant MySQL database ring, so the OpenSER queries always to the primary DB unless it fails. When the "master" database dies, a monit process detects the failure and modify properly the database entry in the DNS zone file. We have tested this redundancy in two way I expose you here: - mysql process is killed in the database host machine. In this case OpenSER realizes the failure and asks the DNS inmediately for the database IP address and the service keeps working as expected. No problem here. - shutdown the interface of the machine where mysql is hosted. In this case OpenSER does not ask the DNS for the new address. It keeps trying over and over the connection with the master and until the interface is not turn on the system keeps hung. The difference between the two cases is that in the first case, the host machine responses with an ICMP (port destination unreachable) when OpenSER queries the database. In the second case we have no answer from the MySQL host machine. So, if the mysql's host interface is shutdown the system hangs but if the mysql process dies the system works properly. In the first case both machines (OpenSER and MySQL) has IP visibility, not in the second, so the problem should be related to that. Do you know why this is happening? Might you, please, be so kind to tell me how to fix this problem or at list how to take a workaround to get it working properly?