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Old April 7th, 2021, 05:40 AM   #1
olivier_vl
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Can't connect anymore [CP1L]

Hello everybody,

I'm using a Cp1l-EM40 PLC for my projects and this morning I changed the PLC IP from 192.168.250.2 to 169.254.67.1, because I needed to test something... My laptops IP is 169.254.67.105, so it should have been in the correct range. However, I can't connect to my PLC anymore. CX-programmer gives the error: Failed to connect to the PLC. Is there a way to change the IP back to 192.168.250.2?

Thanks!
Olivier
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Old April 7th, 2021, 06:28 AM   #2
Wasan
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Quote:
Originally Posted by olivier_vl View Post
Hello everybody,

I'm using a Cp1l-EM40 PLC for my projects and this morning I changed the PLC IP from 192.168.250.2 to 169.254.67.1, because I needed to test something... My laptops IP is 169.254.67.105, so it should have been in the correct range. However, I can't connect to my PLC anymore. CX-programmer gives the error: Failed to connect to the PLC. Is there a way to change the IP back to 192.168.250.2?

Thanks!
Olivier
Maybe this link help you by use direct connection with your PLC.

https://www.myomron.com/index.php?ac...b&article=1487
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Old April 7th, 2021, 06:56 AM   #3
olivier_vl
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Originally Posted by Wasan View Post
Maybe this link help you by use direct connection with your PLC.

https://www.myomron.com/index.php?ac...b&article=1487
Thanks, but i have already tried that and it didn't work.

This is by the way the window I get when I start DirectEthernetUtility.
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File Type: png DirectEthernetUtility.png (20.4 KB, 41 views)
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Old April 7th, 2021, 07:52 AM   #4
drbitboy
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what is the netmask of the PC?
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Old April 7th, 2021, 08:01 AM   #5
olivier_vl
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Originally Posted by drbitboy View Post
what is the netmask of the PC?
Ethernet adapter Ethernet:

IPv4 Address. . . . . . . . . . . : 169.254.67.105
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . : 192.168.250.255

If this is what you meant with (sub)netmask
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Old April 7th, 2021, 08:11 AM   #6
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Quote:
Originally Posted by olivier_vl View Post
Ethernet adapter Ethernet:

IPv4 Address. . . . . . . . . . . : 169.254.67.105
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . : 192.168.250.255

If this is what you meant with (sub)netmask

Yes, and that subnet mask should work. You could try 255.255.255.0, or whatever the PLC was set to be, but it should make no difference.



That default gateway is mis-configured; it should not matter for the current effort, but change it to 169.254.1.1 for sanity's sake.


Do you have access to Wireshark or tcpdump? If the PLC is sending out any ARP or other broadcast packets, you should be able to double-check its IP address.




Try another cable.


Try putting a switch that does auto-negotiation in between the PC and the PLC (requires two cables); perhaps neither side is doing auto-negotiation for the cable pinouts.

Last edited by drbitboy; April 7th, 2021 at 08:18 AM.
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Old April 7th, 2021, 08:26 AM   #7
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Quote:
Originally Posted by olivier_vl View Post
Ethernet adapter Ethernet:

IPv4 Address. . . . . . . . . . . : 169.254.67.105
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . : 192.168.250.255

If this is what you meant with (sub)netmask
Using a 255.255.255.0 is more efficient than 255.255.0.0 , but then the gateway ended with .255 is wrong since the last IP is reserved, it's the broadcast address.

You can also try a port scanner, this works quite well, it can be run without installing it https://www.advanced-port-scanner.com/
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Old April 7th, 2021, 08:52 AM   #8
olivier_vl
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Originally Posted by drbitboy View Post
Yes, and that subnet mask should work. You could try 255.255.255.0, or whatever the PLC was set to be, but it should make no difference.



That default gateway is mis-configured; it should not matter for the current effort, but change it to 169.254.1.1 for sanity's sake.


Do you have access to Wireshark or tcpdump? If the PLC is sending out any ARP or other broadcast packets, you should be able to double-check its IP address.




Try another cable.


Try putting a switch that does auto-negotiation in between the PC and the PLC (requires two cables); perhaps neither side is doing auto-negotiation for the cable pinouts.

That's the 'standard' IP-address. But I dont have Wireshark/tcpdump installed on this laptop, but i will do that the next workday. I have tried another cable already.

Quote:
Originally Posted by lfe View Post
Using a 255.255.255.0 is more efficient than 255.255.0.0 , but then the gateway ended with .255 is wrong since the last IP is reserved, it's the broadcast address.

You can also try a port scanner, this works quite well, it can be run without installing it https://www.advanced-port-scanner.com/
It didn't find any active or inactive networks, so that's weird

Last edited by olivier_vl; April 7th, 2021 at 09:00 AM.
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Old April 7th, 2021, 09:00 AM   #9
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Quote:
Originally Posted by olivier_vl
this morning I changed the PLC IP from 192.168.250.2 to 169.254.67.1
What are the odds that there was a device that was/is using that IP address of 169.254.67.1 and now you have two devices with the same address?

Try unplugging the PLC and PING 169.254.67.1 to see if you get a response
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Old April 7th, 2021, 09:19 AM   #10
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Originally Posted by geniusintraining View Post
What are the odds that there was a device that was/is using that IP address of 169.254.67.1 and now you have two devices with the same address?

Try unplugging the PLC and PING 169.254.67.1 to see if you get a response
Hmm I would be very surprised if there's another device that is using the same IP address.

When I ping 169.254.67.1:
Ping statistics for 169.254.67.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss)
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Old April 7th, 2021, 09:22 AM   #11
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Is that with the PLC plugged in ? unplug the Ethernet cable from the PLC and try it... if you get a response 0% loss then you have another device with the same address and you need to unplug it and change the PLC or use a serial/USB cable to change the PLC
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Old April 7th, 2021, 01:18 PM   #12
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Originally Posted by geniusintraining View Post
Is that with the PLC plugged in ? unplug the Ethernet cable from the PLC and try it... if you get a response 0% loss then you have another device with the same address and you need to unplug it and change the PLC or use a serial/USB cable to change the PLC
Oh yeah, I'm sorry that was with the PLC plugged in. I tried it with the PLC unplugged and these are the results:

Ping statistics for 169.254.67.1:
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),
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Old April 7th, 2021, 02:08 PM   #13
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Perfect, we now know its the only one on the network, I would try the settings below on your PC

IPv4 Address. . . . . . . . . . . : 169.254.67.105
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.250.1

If that does not work, do you have a USB cable? then you can go into the PLC via USB and make the changes
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Old April 8th, 2021, 03:23 AM   #14
olivier_vl
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Originally Posted by geniusintraining View Post
Perfect, we now know its the only one on the network, I would try the settings below on your PC

IPv4 Address. . . . . . . . . . . : 169.254.67.105
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.250.1

If that does not work, do you have a USB cable? then you can go into the PLC via USB and make the changes
I tried those settings, but they didn't work either. I currently don't have an USB cable, because they are at the company itself and I'm working from home... So I think I need to make a ride to get the USB cable.

EDIT: I just tried some other stuff with auto negotation and I was surprised but i was able to connect to the plc!! So thanks!!

Last edited by olivier_vl; April 8th, 2021 at 03:27 AM.
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