Connection Reset By Peer

carson

Member
Join Date
Feb 2011
Location
arima
Posts
22
Good day,

I am currently experiencing a problem with an 1769- L35E controller.
An HMI is connected to the PLC, where both are connected to a DHCP server.
The DHCP server is some how loosing connectivity to the PLC.,thus causing the PLC to loose its IP address.
Is there any way (besides resetting the PLC) for the PLC to re-establish connectivity to the DHCP server, so it does not loose its IP.
 
In general, the CompactLogix should need to access the DHCP server just once after a hard reboot (power cycle).

The PLC will not "lose" its IP address unless it undergoes a reboot.

Something else is going on with your system that is shutting down the controller, the Ethernet switch, or the DHCP server.
 
Is there any setting on the controller for it to retain its current IP. If the switch or the DHCP server has issuses
 
Don't think so....you either set it to a static IP or to Bootp/DHCP. The controller should not lose its IP however unless you lose power to the PLC and the DHCP server is down on power up. Just losing the DHCP server while the PLC is powered will not affect the PLC.
 
Is there any setting on the controller for it to retain its current IP, if the switch or the DHCP server has issuses

I think I see what you're asking for; you'd like there to be a "fallback" IP if the DHCP request fails. Most ordinary computers can do this, with either a preconfigured static IP or using "Automatic Private IP Addressing", APIPA.

I've never seen a Rockwell controller product that has a "fallback" IP or uses APIPA.

I have been in just one factory that used DHCP for controllers and it was... complicated.
 
DHCP is handy for initial setup of the controller, but because it generally requires a third device to be reliably connected to the system, it doesn't make sense for most industrial control systems.

Unless you have a very good reason to use DHCP, set up your controller and HMI for fixed IP addresses.
 
"tell me about it"

The plant I worked in made heavy trucks and had a "reconfigurable" assembly line with workcells that relied on a central DHCP server, a PC running the Rockwell DHCP utility. They also used Host Names instead of IP addresses to identify controllers.

They did this because they wanted flexibility to move around workcells without manually reprogramming the IP addresses. They hadn't reconfigured any workcells in at least 4 years by the time I got there.

But they refused to also install a DNS server (like a Windows 2003 Server) so that the Host Names were resolvable. Instead, every computer had to have a manually updated Host file.

Because the Host file was so labor-intensive to update, most users had resorted to a printout of an Excel file that tracked all the host names and IP addresses in the factory's PLC network. There were about 150 of them.

I also found that they had installed 8-conductor CAT5 cable but split up the conductors so that they could have two 100TX Ethernet runs (4 wires each) in a single 8-wire cable. Each end of such a "trunk" needed a splitter box, and those that didn't have splitter boxes had nonstandard RJ45 color code pinouts. All the switches were Netgear consumer-grade and had no diagnostic or monitoring features, so it was impossible to tell which of these cables was the problem when they had trouble communicating with a device.

All of their RSLogix was pirated off a single license that they'd gotten from a salesman years before. When they ran into a problem they couldn't solve, or needed an upgrade, they started harassing the distributor until they sent a specialist.

After a couple of weeks of working with the guy who had masterminded this system, I presented them with a proposal to upgrade their system to proper switches and cables. Meanwhile I'd updated their archive copies of the PLC programs, upgraded all their engineering workstations to the newest software, removed some viruses, and labeled a few dozen cables.

They thanked us for the report, and refused to pay their invoice, saying that service should be free because they'd purchased a small MCC.

Because they didn't pay their bill, my "utilization" metric dove for the year and I was disqualified from a performance bonus, after I'd been working nights and weekends away from home for a few months straight.

The salesman who sold the MCC got a bonus for signing new business from a dormant account.

So....

I strongly recommend the use of static IP addressing unless you have a very good reason to use DHCP.
 
The reason for the DHCP server is to connect the plc to a red lion productvy station.

Red lion is connected to other PLCs on a 10.3. network and I need it to connect to a PLC on a different network (10.1).
I have to use the company network infrastructure because red lion also logs data that has to be retrieve from other PCs on both networks.
 
Last edited:
HEY,
I put the IP on Static replaced the switch, but i am still getting the connection reset by peer fault {every once in a while} not sure why I still getting this fault. all suggestions are welcome.
 
Hmm, do you know how many network devices are connected to that PLC? They have a limited number of connections they can support. The L35E has a web page built into it to help diagnose problems like these.
 

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