I have a CP343 on a  network that I reach via a router..(TIA v13)

Each time I go online I have to Start Search in the Go online dialog; I select PN/IE and the CP slot/interface.

I get the message

! Assign IP address   

To execute this function the PG/PC requires an additional IP address in the same subnet as the PLC. [Tes][No]

I click[No] and go online

     Why do I get this message?

BTW, clicking [Yes] results in "Adding new IP address failed / IP address already in use [OK] - then I still go online.

Step 7 was much better at remembering how to connect online.

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Split from Access PLC on different subnet in local network.

Not exactly sure the question, but 

the PC is DHCP on another subnet,

the PLC is fixed IP PN/IE on the machine's internal network where all the I/O devices are. There is no routing to other networks from here.

There is an additional ethernet connection via CP343 with a fixed IP on the plant's manufacturing network. This is the connection I normally use. There is a router from the subnet my PC is on to this subnet. The  connection works, but I have to go through the dialog each time. If this were the old Step 7, I could just go monitor online as long as I connect the same way I had the previous time.

Thanks for replying

Thanks Duris_I, 

I checked that the Gateway is set (else it wouldn't work at all), the message that I get is saying that I need an additional IP address. I don't know how that would be accomplished, I only have one ethernet port on my laptop and it necessarily has to be configured for the network I am actually connected to.. 

This is not stopping my work, I just can't figure out why this dialog appears each time I go online.

It seems to me, if I check "No" to the pop-up that is requesting an additional IP address, then it should not work, yet it goes online anyway. 

I can't find settings that seem incorrect, nor would I expect to since the communication works, but the message indicates that there is something not quite right.

Thanks for looking