Siemens S7-400. Error When Going Online

Good Afternoon.

I am having a problem going online with S7-400.

Attached is the error that I am getting.

I have looked at the help file but the solutions don't work.

I can ping the PLC, and it shows in accessible nodes, so I know I have my configuration correct.

Anyone seen this before?

Cheers

Mark

What is S7Online set to in the Set PG/PC Interface ? Is it the same interface with which you can ping the PLC ?
Does the STEP7 hardware configuration of the S7-400 match the actual PLC configuration exactly, especially the port that you use to go online ?

Hi Jesper,

The S7Online is set to the same interface as what I am using to ping the PLC.

I can see the PLC in accessible nodes, and I thought that used the same interface as the S7Online.

The hardware is exactly the same in the offline project as the project I am trying to go online with.

Oddly enough, i just managed to go online, not monitoring though, but after about 30 seconds i got kicked off and now cannot go online again.

is there a way to see the traffic on the ports.

I have been able to access the Web Browser on the PLC.

Cheers

Mark

What is S7Online set to exactly ?
Don't use .TCPIP(auto) or .ISO, unless you have a specific reason to.

Maybe you are running out of connection resources.
But that would stop you from going online at all, not causing you to get kicked off after you have gone online. So I am not optimistic about that one.
Since the webserver is available on the PLC you can go online that way and check the connection resources.

edit: You can try to change the online interface. Add a USB-Ethernet adapter for example.

Hi Jesper,

So turns out I was using .TCPIP(auto).

Changed it to .TCPIP.1 and bingo.

I suppose the next question is why?

I have always used (auto) and it always worked before on different PLC's.

Thanks for your help.

Cheers

Mark

I couldn't find an "official" manual or document that explains the "TCPIP(Auto)" setting, but someone from the Siemens forum wrote the following:

"the Auto setting is made for the situation if your Engineering PC has a different Subnet/IP Range then the System you want to load or connect to. in this case the Auto setting creates temporary a routed IP in the foreign subnet and you can transfer or connect."

I've never used TCPIP(Auto) to connect to S7 PLCs - just TCPIP.1

It is from experience only. My colleagues always uses the (auto) option the first time they use STEP7 and it usually causes problems. I tell them to avoid (auto) and problems disappears.
The explanation from Siemens is not satisfactory.
If the PC is already in the same subnet as the PLC, then there is no need to add an additional IP.
There must be something else going on, but I don't know what it is. Just avoid (auto).

I THINK that the (auto) option gives the same capability that Portals "new" "feature" to automatically add an extra IP to your PC to connect to a PLC in a different IP range.


The downside is it makes routing complicated (impossible?), which is often required in systems.


My opinion is that the best practice remains to be what others have said: don't use (auto), and assign yourself an appropriate static IP.