changing my gateway and subnet mask on a CompactLogix 5323E-QBFC1

I could not connect to or PLC over or network so I checked and the IP address
is correct, but the subnet and gateway are incorrect. It has a HMI(PanelView Plus 1000) connected to through a RJ45 plug I can also see the HMI on or network will I have to change anything on the HMI when I change the subnet and Gateway on the controller and is this something I can do online or will it lose communication with the HMI.

Thanks

If it is currently communicating and you don't change the IP address, you may not have to change the subnet or gateway. It depends on if the new subnet mask is more restrictive than the current subnet mask.

For example 255.255.255.0 is more restrictive than 255.0.0.0. It may also be possible for it to communicate via the gateway if the network is properly configured.

The subnet mask determines what is a 'local' subnet connection. A subnet mask 255.0.0.0 means the first octet of the IP address has to match. i.e 10.1.2.3 can communicate with 10.9.8.7.

A subnet mask of 255.255.255.0 means the first three octets must match. 10.1.2.3 couldn't communicate with 10.9.8.7 because only the first octet matches but it could communicate with 10.1.2.100 because the first three octets match.

If an IP address is not part of the 'local' subnet then data is then sent to the gateway which is hopefully properly to deliver the message.

I'm pretty sure you can't do these online. Even if you do you will likely lose comms briefly.

OK, Thank you for the help