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Old July 3rd, 2008, 07:37 AM   #1
celichi
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Question PanelView Plus ---> SLC L551 Ethernet Communication Issues

Hello fellow techies,

I am using a BSN modules to switch RIO on a redundant SLC500 project (I didn't spec the hardware). The design has one pair of the Ethernet wires going through the 232/485 A and B terminals on the BSN so that the primary PLC would have connectivity to the Ethernet HMIs. For the most part, this works. However, during a failover, I am experiencing communication loss for approximately 7 minutes and 30 seconds. I started to isolate the network, and I am down to the switch, one PLC and the PV Plus. I have disconnected the ME Station, the Secondary PLC and my laptop



Network Configuration

Linksys Switch SRW2008 (10.12.1.1).

PanelView Plus 1000 (10.12.1.13).

Two SLC 500ís 1747-L551 Ethernet. They both have the same IP address, only one is connected to the network at any given time (10.12.1.10).

Dell workstation running RSView ME Station (10.12.1.2).

Programming Laptop is configured as 10.12.1.250

PanelView, Station and PLCs have 10.12.1.1 configured as gateway, and 255.255.255.0 for mask.



Testing

With the PanelView Plus communicating to PLC #1, I can unplug either the PV or the PLC, reconnect, and communication is restored in seconds.



With the PanelView Plus communicating to PLC #1, I can unplug either the PV or the PLC, reconnect to a different port, and communication is restored in seconds.



With the PanelView Plus communicating to PLC #1, I manually unplug PLC #1 and plug in PLC #2 (same IP and program as #1). Communication is dropped and I have 7 minutes and 30 seconds before communication is reestablished.



Everytime I test this, it is around 7 minutes and 30 seconds (+/- 15 seconds).



I have tried different ports, and same ports with the same end result.

I tried forcing PLCs and ports to 100/Full with the same result.I tried using an unmanaged switch/hub with the same result.



If during the PLC swap, I reboot the PanelView (reset switch on the back), communication is restored after the reboot is complete (under 7 minutes).



Best regards,
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Old July 3rd, 2008, 08:54 AM   #2
ghettofreeryder
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I presume the IP addresses are statically assigned. I wonder if it has something to do with Spanning Tree, Do you know if your switches support STP?. If it is enabled, this could be why
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Old July 3rd, 2008, 09:11 AM   #3
celichi
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Yes, all IPs are static.

This SRW2008 does have spanning tree, and it is disabled.



Thanks for your reply, hoping someone else has seen this. Release notes for the F/W upgrade to PVP700-1500_50002.exe on the PV does not cover this problem.

Distributor and AB are stumped.

Best regards,

Paul
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Old July 3rd, 2008, 02:40 PM   #4
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Looks like an ARP table problem in the PV+..stay tuned.
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Old July 4th, 2008, 10:30 AM   #5
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On the PC running ME Station.



I switch PLCs, comms are disrupted.



I open a command prompt, type arp -d, then ping, and communication is established in seconds.



Need to be able to trigger this on comm. Loss and also perform this on PVP 8-).
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Old July 4th, 2008, 02:09 PM   #6
Eddie Willers
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Don't be surprised when the local A-B office doesn't have an answer for you; none of the components your predecessor assembled are intended to work in that fashion. Using the relays on the 1747-BSN to switch between Ethernet cables is... inventive. You should definitely monitor the Station Diagnostics for the Channel 1 port of the SLC to be sure you're not introducing noise and failed packets into the Ethernet channel with this very nonstandard wiring method.

I think that you're right on about the PV+ ARP table requiring a rebuild when you swap devices that have a different MACID and the same IP address. It's just the way that IP works.

You might consider using THREE small switches to do this; one per SLC and one for the PanelView Plus. Manually switch on the power for the switch attached to the Primary SLC controller, and investigate if there's a Windows CE registry entry to cause an ARP flush any time the Ethernet link changes state.
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Old July 4th, 2008, 03:17 PM   #7
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I wonder if you can cause an ARP refresh by manually resetting the SLC-5/05 Ethernet port using a CIP Generic Message to itself ?

Just unplugging it and replugging it probably does not cause it to send out new ARP announcements.

It would be useful and interesting to install a network traffic sniffer in this system (does your switch support port mirroring ?) to see if there is traffic that triggers the ARP refresh inside the PV+, or if the occurence is entirely within the OS.
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Old July 7th, 2008, 07:58 AM   #8
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Great idea Eddie, and it is working now. I am sending out a "dummy" message on the network from the PLC after a switch over. This is updating the ARP tables and restoring communication in seconds!!

Thanks group (especially Eddie) for the assistance!!
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Old August 27th, 2008, 02:26 AM   #9
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Hi Celichi, I predict i may encounter your problem for coming project but my hmi is GE's QuickPanel.

Could you elaborate on the last point how to "triggers the ARP refresh"? Is it done on Windows side and network switch side? Thank you in advance.
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Old August 27th, 2008, 07:11 AM   #10
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Hi CHampion,

The PLC triggers a dummy message (using the MSG instruction), which "alerts" the HMI of the new IP/MAC relationship.

It works perfectly!

I hope this helps.
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Old August 27th, 2008, 10:02 PM   #11
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Yes it's simple but a perfect solution with very short switching time. Thank you for your sharing.
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Old August 28th, 2008, 06:59 AM   #12
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No Problem...Thank Eddie, he planted the seed 8-).
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Old April 11th, 2016, 03:28 PM   #13
JasonPei
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Hi Celichi,

I am having the same issue with my SLC switch-over. Could you please give more info on the "dummy" MSG instruction? is the MSG type peer-to-peer? the target device is PLC5 read, right? Since the commissioning time is very short, any additional info would be greatly appreciated.
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Old April 12th, 2016, 08:22 AM   #14
celichi
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Because I was using this card to switch Ethernet (the MAC address changes).

Just send any messages, doesn't matter what it is, just fire anything out, and this will update the ARP tables.

http://postimg.org/image/baoghkc4h/

Last edited by celichi; April 12th, 2016 at 08:28 AM.
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Old April 12th, 2016, 08:33 AM   #15
celichi
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SLC Export

dummymsg.zip
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