PLC connection failure to PC (ethernet)

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Despy
Posts: 1
Joined: Mon May 08, 2017 4:14 pm

PLC connection failure to PC (ethernet)

Post by Despy » Mon May 08, 2017 4:19 pm

I wouldn't ask for help, but i am completely lost here. Maybe someone could give me some advice. I have a Beckhoff CX5010 and laptop with TwinCAT 3 Engineering software. PLC is in Run mode.
What happens when i connect PLC and PC with ethernet cable:
1) Lan ports LEDs show successful connections
2) PC get IP address 169.254.xx.xx using DHCP. Supposedly right subnet mask 255.255.0.0 for Beckhoff PLC.
3) Using "arp -a" (which will get the list of all IP addresses on your segment) i don't see any other connections.
4) Most confusing. When trying to choose target for TwinCAT software using Broadcast Search for devices. Where i should get CX PLC host name/ip address on my LAN connection. Instead i get my own PC IP address and name.

What i have tried and always same results:
1) Different Straight-Through and Crossover Ethernet cables.
2) Disabling DHCP and setting up manually different IP addresses with 169.254.xx.xx IP and subnet 255.255.0.0

Some screenshots to give you some overview what is happening:
http://i.imgur.com/gICmaaP.png
http://i.imgur.com/wkp97X0.png
http://i.imgur.com/bWbAIIE.png
I really hope someone can help me.

almaz78
Posts: 108
Joined: Tue Dec 16, 2008 7:36 pm

Re: PLC connection failure to PC (ethernet)

Post by almaz78 » Mon May 08, 2017 6:37 pm

read this. it explains why you end up with ip 169.254
https://askleo.com/why_cant_i_connect_w ... p_address/

from the above link
When there’s no answer

This difficulty arises when your computer asks for an IP address, and no one responds to the request.
Whether due to a network problem, maybe not being on a network at all, or perhaps there’s no DHCP server to hand out IP addresses, the result is the same: the request for an IP address assignment goes unanswered.
Your machine waits for a while, and then gives up.
But when it gives up, it invokes what’s called Automatic Private IP Addressing, or APIPA, and makes up its own IP address. And those “made up” IP addresses all begin with 169.254.
to connect to your PLC:
1. find out IP address of PLC
2. manually set Laptop IP to be on the same subnet
3 connect using crossover cable

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