Siemens S7-1200 is losing network

Yashka

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Join Date
Nov 2019
Location
WV
Posts
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Hi All
I have a baghouse control system in production for many years. But some time ago the PLC began to lose the network suddenly until I restart by power switch off/on. It seems like the Ethernet port is going down and no one outside (HMI panel, Profinet devices, etc) doesn't see the PLC. The diagnostic buffer has contained only network errors for Profinet devices and nothing else.

The PLC is 6ES7 215-1HG40-0XB0 with firmware 4.2, occupied memory is less than half, CPU load < 10%, any ideas?

Thanks in advance!
 
You say it is the Ethernet port going down, but it could equally be an Ethernet cable problem, or whatever the other end of the cable is attached to, problem (Ethernet switch?). As there isn't an 'easy' way to try to diagnose Ethernet problems I tend to go with the 'swap out the cheapest' things first option. So try another port on the Ethernet switch, then swap the cable, then swap the PLC or Ethernet switch.
 
Yashka said:
It seems like the Ethernet port is going down and no one outside (HMI panel, Profinet devices, etc) doesn't see the PLC. The diagnostic buffer has contained only network errors for Profinet devices and nothing else.
Click to expand...
Do you go online and check the diagnostics buffer before or after the power cycle ? If you can get access with TIA then the port is not offline.

Is there a switch in the system ? Cheap unmanaged switches can be overwhelmed by Profinet traffic.
Can you check by removing the switch and connect directly to the S7-1200 ?

It is possible that some HMI or other device has a problem and try to setup too many connections, or do not release connections. That may cause the PLC to run out of connections. There should be 1 reserved PG connection, so you should be able to get online and check diagnostics buffer and the available connections.
 
BryanG said:
You say it is the Ethernet port going down, but it could equally be an Ethernet cable problem, or whatever the other end of the cable is attached to, problem (Ethernet switch?). As there isn't an 'easy' way to try to diagnose Ethernet problems I tend to go with the 'swap out the cheapest' things first option. So try another port on the Ethernet switch, then swap the cable, then swap the PLC or Ethernet switch.
Click to expand...

This is one of the biggest wonder things for me. The log from CISCO didn't show that the port has been down. The physical layer was okay. Something has happened on the upper layers.
 
JesperMP said:
Do you go online and check the diagnostics buffer before or after the power cycle ? If you can get access with TIA then the port is not offline.
Click to expand...
Unfortunately, no. I'm asking employees to call me when it's happening but every time they didn't it.

Is there a switch in the system ? Cheap unmanaged switches can be overwhelmed by Profinet traffic.
Can you check by removing the switch and connect directly to the S7-1200 ?
Click to expand...
We're using only managed CISCO switches on our plant with special VLAN for such equipment.

It is possible that some HMI or other device has a problem and try to setup too many connections, or do not release connections. That may cause the PLC to run out of connections. There should be 1 reserved PG connection, so you should be able to get online and check diagnostics buffer and the available connections.
Click to expand...
Thanks for the great idea. If some equipment doing very fast reconnect cycles it could cause a "no more connection available" state in the kernel. I didn't think about it before. How I can see all incoming and outgoing connections from TIA? Is it possible to monitor these remotely?
 
Yashka said:
We're using only managed CISCO switches on our plant with special VLAN for such equipment.
Click to expand...
I would not trust the switch. When the error situation is active, dont reset by cycling the power. Instead disconnect the switch, connect a laptop directly and try to ping, try to go online with TIA, and/or try to access the webserver.
edit: One more thing to check is if the CPU appears in the "accessible nodes" list of devices. This method reaches the CPU via the MAC address instead of the IP address.

Yashka said:
How I can see all incoming and outgoing connections from TIA? Is it possible to monitor these remotely?
Click to expand...
When online with TIA, in the project tree left side, select the CPU, and in the Properties select Diagnostics tab, Connection information.
edit: Possibly you can also see this via the webserver. I havent tried that myself though.
 
Last edited:
JesperMP said:
I would not trust the switch. When the error situation is active, dont reset by cycling the power. Instead disconnect the switch, connect a laptop directly and try to ping, try to go online with TIA, and/or try to access the webserver.
edit: One more thing to check is if the CPU appears in the "accessible nodes" list of devices. This method reaches the CPU via the MAC address instead of the IP address.

When online with TIA, in the project tree left side, select the CPU, and in the Properties select Diagnostics tab, Connection information.
edit: Possibly you can also see this via the webserver. I havent tried that myself though.
Click to expand...
Thank you, I've found those tables. But one question left - how to reach that info from the user program for logging/monitoring purposes? Is it possible?
 
Yashka said:
Thank you, I've found those tables. But one question left - how to reach that info from the user program for logging/monitoring purposes? Is it possible?
Click to expand...
Unfortunately I am not aware of that.
There are plenty of examples on how to get hardware errors via GET_DIAG, but I dont know how to query the no of available connections from the user program. I would be interested in that myself.
 
JesperMP said:
Unfortunately I am not aware of that.
There are plenty of examples on how to get hardware errors via GET_DIAG, but I dont know how to query the no of available connections from the user program. I would be interested in that myself.
Click to expand...

I watch during some time current connections (see attachment). And I have doubts that it is the root cause of my issue. It seems to free resources enough.

S71200_Connections.png
 

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