Mitsubishi MELSEC QJ71MT91 Modbus TCP slave communication with Redundant Modbus TCP master stops dur

[yalawani 0]

Configuration used: We are using our Modbus TCP master to communicate to Mitsubishi MELSEC QJ71MT91 as Modbus TCP slave. We are able to communicate with the QJ71MT91 Modbus TCP slave. Our Modbus TCP master is redundant module. That means that if the primary master fails then there a switchover to the backup master. An IP address swap takes place for the master during the switchover. So the new primary after switchover shall get the same IP address as held by the old primary before switchover. Problem: When Ethernet cable from primary master is removed, there is a switchover to the secondary master. It is expected that after switchover the communication with the QJ71MT91 s;lave should continue. However we see that after switchover, the new primary master send connections request to the QJ71MT91 Modbus TCP slave, but the QJ71MT91 still sends response to our old primary master only. Hence the communication of our Modbus TCP master with the QJ71MT91 Modbus TCP slave stops. We are sending the gratuitous ARP messages to the QJ71MT91 slave to update its ARP table during switchover, but it seems that the ARP table does not get updated on the QJ71MT91. We donot get the problem if we use any other slave connected to our Modbus TCP master. Is there any setting on the QJ71MT91 for slave configuration to resolve this issue?